This is leading towards a debate over whether two matched cardioids
are in fact a truer match than either side of a fig-8. I'm of the
opinion that the matched card's are a truer match, mostly because you
can't as easily test the internal bipolar matching on a mic-by-mic
basis like matching two card's.

May I take a closer look at this rather mysterious course of logic? If
I didn't know better, I'd think you were saying that the ease of testing
which you imagine in a thought experiment (!) should take precedence over
the accuracy of competent real-world measurements.

[snip]

Reversing cardioid signals is hardly experimentation. Two card's can be
trusted as a 100% match when they produce no perceivable signal when one is
inverted against the other. That catches aspects that aren't even
understood, much less measureable. That is a far more reliable test than
any that can be applied to a fig-8, except if you had a matched pair of fig
8's that stay matched if you turn one around, something I've never heard of
happening. If you reverse one or both of the fig-8's in Blumlein format
you'll get different imaging every time. The dependence on a balanced fig-8
in MS format is equally severe.