>>50837067Each save file has a different set of exclusive items that you need to trade with other players to get the other ones.
It's like if you started a Pokemon Gen 1 game and instead of getting Electabuzz, Scyther, and Mankey every time your save could have a combination of Magmar, Scyther, and Mankey instead. You'd need to trade with a lot more people to actually find the Pokemon you need for your dex instead of just getting the 2nd version. In Pokemon they could use this to only have 1 version and make those not tied to the save file either super rare like PLA or not show up at all like normal.