Honestly not even sure I'd say this is an actual annoyance, but "Funny thing that annoys me" has a better rhythm to it so...
Did You Know? If you don't start the Peony questline properly -that is, going through the first Dynamax Adventure and getting the whole thrust of the legend plot going- there is one fly point available to you? The station and only the station.
The Regi temples? Nothing, even if you inspect their doors. They don't even get marked on your map
The town? Even if you go into the Inn and rest up, it won't be marked as flyable.
The Watt Trader? He isn't there!
Did you treck all the way up to the Crown Shrine? Even get the cutscene with the horse watching you? Go into the Shrine proper? Still does not count.
The only major fly point I didn't go to was the Dynatree and that's mostly because I don't think you can get there without the water bike. But considering nothing else activates I doubt it.
It's really interesting that they even let you explore like that but dont enable anything. I can understand, to an extent, anything related to the legendary Pokemon. Perhaps they want to make sure the intro cutscenes play properly? But there's really no reason to not let you fly to town or to not spawn the watt trader, personally.
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But related to the Tundra. So it's clearly intended as a mix of late-game to post-game content. Peony's level 70, all the Legendary Pokemon are level 70, all the wild Pokemon are locked to 60s, the Pokemon you get out of the Adventures are all about the same level, capturing Calyrex requires beating Leon.
But they still let you go there anyway, which is fine. They opted for the "you paid for this, so you should be able to access it without waiting too long" side of DLC rather than "you must complete the game first" for it that some games do. So you can lose to Peony and still start the various quest lines and even do Adventures (and they get to obey you too since they circumvent the capture penalty) if you really want to power game, etc.
But like....di you know that the raids still scale to your progress? So if you do it at the start of the game, all the raid dens will have 1 star Pokemon at level 15? At that point why NOT have the wild encounters scale to your progress in the same way the Wild Area and Isle of Armor do? The legends can still keep their high levels, that's fine, but...weird right?