When you explain away the lack of slash pairings in shonen with “it’s a shonen”, you don’t really say that “it’s for young boys.”

You say “it’s for young STRAIGHT boys.” You erase the young boys who still don’t often see their romantic alignment seen as natural.

You still treat heterosexual romance as “pure and normal” and homosexual romance as “18+ and unnatural”.

A boy can still go an an action packed adventure and save his world and fall in love with another boy.

Same goes for girls, of course.