Sometimes the rules in games assume that you can make an intuitive leap. This is one of those times. This part of the rule book is talking about disengaging strikes and never mentions any model not engaged by an enemy. You are absolutely correct in the whole RAW bs argument, but t is just that. BS.
I've not yet come across a game that has lots of RAW vs RAI arguments, but Malifaux is very close to being that game. Rules forums don't need a Devil's Advocate and it would be super awesome if you could stop being that guy, because yo seem to have an excellent grasp of how the game works.