People created this imbecile headcanon that "zoro always fight stoic characters, while sanji always fight clown characters" as some ironclad rule.
It's not the case.
It's never been the case.
In the end, it's nothing more than some headcanon way to "downplay sanji" because, in their minds "clown characters = weak characters".
Imagine thinking that's the case in a manga like One Piece, when 90% of the characters have some retarded/childish gag.
It's the edgelord syndrome.