bainsey wroteI have to wonder if it's more like blatant ignorance, rather than misunderstanding. Otherwise, why would we get the "set" argument if they even know about verticality?
Because, while the terms are linked in the book, they aren't linked in the minds of most players and coaches. When they argue a player wasn't set, verticality is rarely an issue anyway because the player was moving sideways or backwards (usually).
I have never heard a coach argue a defender was moving when he simply jumped vertically.