If the adversary wants to flee from combat, but can't take up a defensive stance, then what?
From p104 under heading "Fly, You Fools!"... "They can first assume a Rearward stance, and then choose to escape when their turn to act comes. No roll is required to do so.
The same applies to adversaries who chose to stand back and thus remained unengaged.
Well, that's the whole conundrum. Adversaries do not use stances, which precludes them from escaping unless they are unengaged - if you follow RAW. Unless I've missed something! I would however go with using the similar mechanics. The trick is though that there are combat modifiers in a defensive stance that are relevant, so it becomes and odd exception.