>>49997860Not including Red makes sense because none of the protags who become champion are included. Not even Elio/Selene, which means no Alola League representation at all, since there's no other true champion there besides the player character.
Including Blue makes sense because he became champion right before (You) show up, meaning he's the one you have to fight for the position. Including Lance makes sense because he was champion in his own right and (You) fought him for the title in Gen 2. Red at this time had already abandoned the Indigo Plateau and discarded the title. Likewise Steven makes sense because you fought him for the title, same with Wallace. And same with Iris.
Which leaves Alder, who was defeated by N before you got there. So technically N is the one holding the position of champion before you beat it out of him. That's the difference between Alder and everyone else in that picture. He was champion, but you didn't defeat him for the title; you defeated N who'd recently usurped the position, sort of like Blue in the first game.