Oh, absolutely no means no! I think that the point here is that it is not the "other couple" that will break the rule, but half or both of the rule-making couple itself who will not be able to keep the rule. Therein lies the drama, as many many threads on this site can attest to.
I know that we would steer clear of a couple that had those sort of potential drama bombs as rules. (not to mention that playing with a no-kissing couple, as we did in our newbie days, was just too hard. Complying with the other couple's rule was a given, as far as we were concerned, but the effort required to comply with the rule interfered with our enjoyment of the activity.)