OK so I thought maybe my earlier posts could still be a little confusing, so to the best of my understanding, this is how the games work
Let's just say we have the Pokemon file for a Dialga from DP. A moveset for Return, Hidden Power & Roar of Time.
If we were to directly "insert" this Pokemon file into a gen 8 game, what happens? For this purpose we'll just ignore questions of file formats and expanded data that happens between games.
What Home does is basically do the insertion for you. If the last update hadn't happened, the Dialga would work as it does in all 3 games above.
But the update did happen. So what happens when it moves this DP Dialga to the games now?
Home marks the moveset in its own memory, wipes the moveset if it's the first time it happened*, then "places" them into the game with the default level up for that game. If it's going in & out between games, Home will remember the respective game's respective moveset that you gave it and restore it to that for that game as needed. As far as I know this is entirely on Home's end.
*The exception to this, iirc my own testing on it, is if a pokemon comes from pre-gen 8 and goes into SWSH. It will just retain everything about itself. Probably just to keep parity with how it worked before.
Let's just say we have the Pokemon file for a Dialga from DP. A moveset for Return, Hidden Power & Roar of Time.
If we were to directly "insert" this Pokemon file into a gen 8 game, what happens? For this purpose we'll just ignore questions of file formats and expanded data that happens between games.
- SWSH. Return & Hidden Power, internally, aren't usable and have a "Please delete, maybe" message. The game will not force delete them. You must do that. Roar of Time is left alone. The listed moveset is thus still "Return/Hidden Power/Roar of Time"
- BDSP. Return isn't usable and has a "Please delete, maybe" message. Hidden Power can't be taught to anyone in BDSP, but the move itself is still usable and there's no "Unown only" flag or anything. Thus your Dialga can still use it just fine. The game will still not force delete either move. You must do that. Roar of Time is also left alone. "Return/Hidden Power/Roar of Time"
- LA. Same as BDSP. Though truth be told I'm not actually sure if Hidden Power might've gotten an "Unown Only" flag, but regardless the move would display just fine; if it was somehow Unown only it would simply fail when you try to use it.
What Home does is basically do the insertion for you. If the last update hadn't happened, the Dialga would work as it does in all 3 games above.
But the update did happen. So what happens when it moves this DP Dialga to the games now?
Home marks the moveset in its own memory, wipes the moveset if it's the first time it happened*, then "places" them into the game with the default level up for that game. If it's going in & out between games, Home will remember the respective game's respective moveset that you gave it and restore it to that for that game as needed. As far as I know this is entirely on Home's end.
*The exception to this, iirc my own testing on it, is if a pokemon comes from pre-gen 8 and goes into SWSH. It will just retain everything about itself. Probably just to keep parity with how it worked before.