Pokemon Legends: Arceus is a valuable new entry in the franchise because of how much it contributes to the franchise's overarching lore. Most Pokemon games share a time period, which means fans only get glimpses of the Pokemon world's history through ancient ruins and stories told by certain NPCs. Pokemon Legends: Arceus puts players right in the middle of Pokemon history instead, detailing how Sinnoh became a united region and where Sinnoh's very first Pokedex started. Interestingly, Game Freak has taken Pokemon Legends: Arceus as an opportunity to not only contribute new things to Pokemon history but to retcon a few parts of the franchise's lore as well.
At the beginning of the game, players meet a Pokemon professor as usual. Professor Laventon provides players with an explanation of how Poke Balls work and introduces the player to the Pokemon world. In the process, longtime Pokemon players might notice that he says every Pokemon has the ability to shrink to a tiny size, which certainly hasn't come up in previous installments. The change helps explain how old-fashioned wooden Poke Balls can capture monsters, but it doesn't make a ton of sense on the whole. Game Freak may have written itself into a corner by giving all Pokemon this strange ability.
The Poke Ball Retcon
Historically, Pokemon has maintained that Poke Balls convert Pokemon into energy when they capture a monster. That explanation stands to reason: Poke Balls are high-tech sci-fi devices that could pull off a feat like that, and converting Pokemon into energy also explains how trainers can store spare Pokemon in a PC. However, Pokemon Legends: Arceus takes a very different angle. Pokemon physically shrink down to minuscule size when they're hit with a Poke Ball. The change helps explain Pokemon Legends: Arceus' Poke Balls since they're much simpler devices made from Apricorns, but it raises a lot of questions.
For one thing, if Pokemon simply shrink down to fit inside a Poke Ball, that would suggest that they're always rattling around the inside since there's no evidence that old-fashioned Poke Balls hold Pokemon in place in any way. That sounds pretty unpleasant for a tamed Pokemon, especially when the trainer constantly throws the Poke Ball at things. If Pokemon can shrink down to microscopic size at will, that also begs the question of why many Pokemon bother physically running away when they could just shrink down immediately to get out of danger.
The Impact on Future Pokemon Games
The Poke Ball lore change is particularly strange because it's hard to say if it'll actually have any effect on future Pokemon content. Technically, there's nothing stopping the Generation 9 Pokemon game from making Poke Balls turn Pokemon into energy again, since players will be using high-tech Poke Balls again. In that case, the lore change would essentially be forgotten. On the other hand, it could also take the concept and run with it, emphasizing that Poke Balls still work this way, but have technological improvements that accommodate the shrunken Pokemon better, preventing them from bouncing around inside the ball and simulating a comfortable environment.
Poke Ball mechanics probably won't change too drastically from the lore change, nor does it seem likely that future Pokemon games will feature battles where monsters learn to tactically shrink and grow to avoid attacks. That simultaneously makes the change less significant and more bizarre. It's a major rework of a fundamental aspect of the Pokemon world, and yet there's not really any reason to think that Game Freak will make major changes to other parts of Pokemon to justify this new power that all Pokemon share. Pokemon Legends: Arceus isn't necessarily made worse by its new approach to Poke Balls, but it's certainly made stranger.
Pokemon Legends: Arceus is available now for Nintendo Switch.