It seems to me that inverted form stability is important--and morbidly fascinating--but only relevant in a small portion of the cases of boats that are knocked down past 90 degrees.
Anecdotal evidence (is there any other kind in matters like this where the sample is so small?) is that most boats knocked down below horizontal come up one way or the other--if they come up at all--and right themselves. Often without masts and deck gear including deck structures.
I think the more interesting question is how to balance in a useful sailboat the attributes of initial stability, ultimate stability, ballast, beam, draft and hull volume. And for the boat owner/buyer, how to make a reasonable judgment of stability for themselves. While the screening formulas for stability are very simple they do give amateurs (most of whom won't be getting an IMS certificate) some notion of the factors involved. If the present screening formulas are inadequate maybe someone could come up with one that could be done with ordinary lines plans, boat specs and a pocket calculator. Or is there already such a formula?