Out of curiosity, can anyone confirm whether Shell Side Arm's only options are full physical or full special?
This post seems to suggest that it can also mix and match Defense and Special Attack (like Psyshock) or Attack and Special Defense:
I haven't really seen anyone follow up on this, either to confirm it or deny it - it seems like most people are still operating under the assumption that this isn't possible/that it always uses matching Attack and Defense stats, but I'm not sure if this was actually proven wrong or if it was just overlooked.
I would really like to see this tested if possible!
That's essentially my theory after testing this a few days ago. For the sake of bringing this topic back up, I'll recall what happened during those tests.
I had a Galarian Slowbro at Level 55, and my targets were Level 60 Chansey. My first test was to have my Slowbro use a Modest nature and max Special Attack EVs and no Attack investment. My Special Attack was in the 170s, while my Attack was in the 110s. I wanted to see if Shell Side Arm worked like (but not exactly like) Psyshock, where the attack pulls from the Special Attack stat and attacks the opponent's Defense if it happened to be lower than the Special Defense. During this test,
Shell Side Arm used the physical animation, and my Slowbro OHKOd the Chansey, confirming my suspicion. I'm not convinced that when Shell Side Arm shows the physical animation, it's directly pulling from the Attack stat itself because let me pull up this calc again:
Lvl 55 0- Atk Slowbro Poison Jab vs. Lvl 60 0 HP / 0 Def Chansey: 225-265 (57.9 - 68.2%) -- guaranteed 2HKO
Again, this assumes Slowbro is Poison-type, has an Attack stat of 100, and Poison Jab is 90 BP. This is nowhere close to an OHKO, but my opponent Chansey was OHKOd regardless while I was using 252 Special Attack, a Modest nature, and 0 Attack EVs.
My next test was to see if Shell Side Arm only ever pulled from the Special Attack stat at all, considering it's listed as a Special move in its description (similar scenario with Psyshock and Necrozma's Photon Geyser). I used a bunch of Hondew Berries to remove the SpA, used an Adamant mint, and pumped 252 Attack EVs. The stat numbers this time were the same as before but in reverse, with the Attack being in the 170s while the Special Attack was in the 110s.
Once again,
Slowbro used the physical animation for Shell Side Arm and OHKOd Chansey.
Here's the calc for Shell Side Arm vs Chansey when the Attack stat is factored in:
Lvl 55 252+ Atk Slowbro Poison Jab vs. Lvl 60 0 HP / 0 Def Chansey: 348-409 (89.6 - 105.4%) -- 37.5% chance to OHKO (the Chansey in the wild most likely had less Defense IVs than 31 because they consistently got OHKOd)
From my perspective, this move is extremely smart. It seems to be using Galarian Slowbro's highest attacking stat, whether it's from its Attack or Special Attack stats, and translates that higher stat number to either physical or special damage depending on which defensive stat from the opponent is the lesser of the two. It's like a much better version of Photon Geyser that adapts to the situation at hand. I'd also like to see more people test this out to see what they think about all this.