>>58256200
crossgen babymons albeitdoe

For those who don't know, OP's image is from this:
https://www.pokemon.com/uk/pokemon-news/marvel-at-the-middle-evolution-pokemon-infographic

A page on the official Pokémon website showing appreciation for middle stage Pokémon. It's really strange that they don't consider the Pokémon that OP's pic shows to not be proper middle stage Pokémon just because their pre-evo is a cross-gen pre-evo. Yet Pokémon who are middle stage, yet whose evo is a cross-gen evo are counted.

>>58257544
I believe its because their pre-evolutions aren't "pre-evolutions" but "babies" which is a loose category of pokemon we rarely see mentioned nowadays since they stopped doing it after gen 4, but there was a clear distinction between "baby pokemon" and first evolutions because baby pokemon can't breed.
Therefore, I believe the category is easy, a middle stage pokemon is a pokemon that can evolve that evolves from a pokemon that can breed, meaning they are the 2nd fertile stage of the pokemon.

>>58257592
Toxel is a baby Pokemon so they made one in gen 8

and no, this isn't about baby forms, Togepi and Riolu are babies, but becuase they're introduced with their evolved form, they dont belong to this weird group