>>47004953Being games of different genres and subseries, spin-offs have some different parameters for quality than the main games, yes. Particularly, core Pokémon games have had connectivity that allowed you to send old Pokémon up to the next new game in the series since DP and maintained that until SS.
Spin-offs are not and never have been part of that continuity between the main games (except for the two GameCube games, which also allowed use of all existing Pokémon at the time), therefore there is no need for them to include every Pokémon.