I think the distinction is using the hook when the player has already gone. If, for instance, someone has fairly beaten or dispossessed you by dribbling or a bb shot, then hooking them as they pass you seems to me to be pretty unsportsmanlike. If you are directly competing for the ball or are in a position to block a player with a shot on, then I think a hook can make sense. I have obvious reservations about reaching over someone's mount to effect the hook or block.
I think the distinction is using the hook when the player has already gone. If, for instance, someone has fairly beaten or dispossessed you by dribbling or a bb shot, then hooking them as they pass you seems to me to be pretty unsportsmanlike. If you are directly competing for the ball or are in a position to block a player with a shot on, then I think a hook can make sense. I have obvious reservations about reaching over someone's mount to effect the hook or block.