I want to jump back to this for a moment to mention that Pikachu got Icicle Crash before Kyurem, despite the former having literally no logical way to produce Ice compared to the latter producing it for several of its signature moves.
Note only Cosplay Pikachu could learn Icicle Crash and only as Belle Pikachu as it represented the Beauty category which a lot of Ice-type moves are classified as (and they wanted to have each Cosplay Pikachu special move be a different type). Maybe the costume in some way allowed access to the move, like it generates cold to keep Pikachu from overheating in it and Pikachu can use it as an attack.
But Icicle Crash always had a poor distribution for no reason. Only Pokemon that can learn it are:
- Level-Up: Alolan Sandslash (though needs to be relearned), Cloyster, & Beartic
- Breeding: Alolan Sandshrew, Sneasel, & Swinub
The requirement for Icicle Crash isn't quite clear. Honestly it would seem any Physical focused Ice-type would be able to learn it as the animation is just it creating icicles over the opponent. Many of the Pokemon seem to have spikes (or tusks in Swinub's case) as part of their design or evolution's design, though Sneasel family don't but they learn it (they do have long sharp claws). Then again Egg Moves were always given some wiggle room.
But, with that all said, I see no reason why Kyurem, Snorunt/Glalie, Bergmite family, or the Snow family can't learn Icicle Crash. They're Physical focused Ice-type, are able to create air cold enough to freeze, and have spikes (or are just jagged) somewhere on their design or evolution's design.
Curious if it was maybe originally meant to be Beartic's Signature move but GF also let Cloyster get it upon discovering it doesn't have a strong physical Ice-type move (no, only Shellder learns Icicle Spear, also what if you don't want to use a Cloyster with Skill Link?... Okay, you can stop laughing now...).
And this is tangential at most, but what makes an Ice Attack Physical vs Special anymore? Until now I believed enough that the distinction was a simple enough "Physical Ice vs Cold Air" distinction, but Kyurem's Glaciate in B2W2 is depicted as forming Icicles to spear the player with in cutscenes, which if nothing else entails that the "Cold Air" moves could just as easily form solid ice by freezing airborn water, at which point why does the distinction mean anything? What stops an Articuno from smashing Chansey by freezing air to drop Ice instead of trying to ice Chansey directly? In fact that seems like an interesting idea for an Ice type Psyshock clone.
Yeah, it makes no sense Glaciate did that as this is Glaciate's move description: "The user attacks by blowing freezing cold air at opposing Pokemon". Would have probably made more sense if giant icicles formed around the player forming from the ground like stalagmites to physically trap the player with the danger of it freezing the center where you're in. But the animators wanted to be a bit more show-y (or didn't read/care about the move description) and have it creating and controlling icicles even though that makes no sense in context to the move.
But you're right that, from what it looks like, the main distinction between a Physical and Special Ice-type move is that Physical uses frozen water in some way and Special is just cold air/energy (don't think about the science behind that it'll just make your head hurt). The only exception to this is Powder Snow, though the move's description is "The user attacks with a chilling gust of powdery snow", so it is still cold air but just has snow in it.
Category Confusion:
Though this did make me curious: are there other moves which may have category confusion? So I decided to check the other Types and this is what I got:
Normal:
Explosion & Self-Destruct (Physical): Special Normal-type moves are either about noise or just energy. So why are moves which idea is they're giving off massive amounts of energy Physical? Like, is it the shrapnel the danger here?
Natural Gift & Secret Power (Physical): Here more due to vague name and description. They draw their power from either a Berry or the environment, and that's it. Like these could be made Special moves and no one would have noticed.
Present (Physical): So how does the present do damage? Do they explode (which in that case would be energy)? Does a boxing glove on a spring punch the target in the face (which would be physical)?
Wring Out (Special): How is a move that grabs the opponent and tightly squeeze them consider a Special move?
Fighting:
Force Palm (Physical): Here because of its description: "The target is attacked with a shock wave". Wouldn't that be more of a Special move than?
Bug:
Infestation (Special): How is sending a swarm of bugs to cling to your opponent and damage them (presumably by biting/scratching/stinging) be Special?
Struggle Bug (Special): "While resisting, the user attacks the opposing Pokemon". What is this move doing? Like who's resisting, the target or the user? And still, in what way are they attacking that it's considered a Special move?
Steel:
Metal Burst (Physical): "The user retaliates with much greater force against the opponent that last inflicted damage on it". Here for vagueness, how is it retaliating? Is it throwing a metal object at them? tackling them? Steel energy (which would more be a Special move)?
Fire:
Fire Lash (Physical): Heatmor's Signature Move, it's an odd one (not only because its an obscure Pokemon that got one two generations after its generation). Idea is I guess Heatmor is attacking with its tongue, but Heatmor doesn't really have a tongue but rather a flamethrower (its Special Attack is also higher than its Attack). So is it solidifying flames to make a tongue to do a 80 Power move off its weaker attack instead of a 90 Power Flamethrower off its stronger offense stat? Sure it decreases Defense but whether the opponent cares about that is just as situational.
Sacred Fire (Physical): Like, I get why, Ho-Oh's Signature Move and it has a high Attack stat, but could they at least say it covers its body with flames and than attacks? All its description says "The target is razed with a mystical fire of great intensity". Or since its mystical it can do whatever it wants?
Grass:
Grass Knot (Special): Wouldn't making your opponent trip and fall be Physical?
Leaf Storm & Leaf Tornado (Special): This is where it gets tricky. All other "leaf" moves are considered Physical since leafs are a physical object, only other exception being Magical Leaf but it's leafs covered by MAGIC so that explains that. So why are these Special? Is it because it's not the leafs doing the damage but the wind force that causing the leafs to whirl around? Then what do the leafs got to do with that then, isn't that just a Flying-type move than?
Petal Dance (Special): Same issue as above except with flower petals instead of leafs.
Alright, not too bad overall. The most confusing ones are Wring Out, Infestation, and all the Grass-type moves, but I guess you could justify it by saying it was just filling a gap so wasn't meant to be thought heavily upon.
