(the entire set of assumptions does not break down for poly relationships or relationship-anarchy, but it gets more complicated).

I tried to mention this above; but didn't want to cover it entirely as its no longer part of the largest subset of people to which the rules can apply, and requires specific considerations for this set. I would rather leave it as an un-tackled piece than a badly-tackled piece.

It seems that several of the "edge but big enough" case have been brought up by people in relation to what has been missing from my set of rules-to-try-to fit to. I considered these edge-but-big-enough cases not big enough to mention; but I suspect individual variation on these considerations causes people to define big-enough differently and decide them to be more worth mentioning. This is an interesting pattern to note and in future I will list edge cases that I have acknowledged but not tackled in the main post.