A 50:50 mix of a mid cardioid with the side fig8 would (with ideal card/fig8 mics) yields a crossed hypercard pattern, but with an included angle of 120 degrees. The relative mix creates both the pattern and the angle, and of course MS is a coincident mic pattern. To get an angle of 90 degrees, yields something like a subcard pattern.
If you do the maths, a 1:1 M/S mix of an ideal cardioid and Fig-8 actually translates to a virtual XY pair of included angle 126.9 deg.
And this virtual mic has a "V=a + b.cos(theta)" polar pattern of V = 0.309 + 0.691.cos(theta).
So It's quite reasonable to label such an outcome as "supercardioid". Various literature sources - Woram, Witteck (Schoeps), Jecklin, Sengpiel, Eargle, Dooley & Streicher etc - list a supecardioid as having "a" ranging from 0.33 to 0.37, with "b" from 0.67 to 0.63. A hypercardioid is generally put in the ballpark of "ä" = 0.25 and "b" = 0.75. The MK41 is supercardioid.
All academic of course, for we never have perfect mics. [and my nitpicking about names reminds me of those German technical hobby mags - Hi-Fi, photo etc.- where a stressed reader would send in a letter with: "Please help. I can't sleep! Please clarify: is Model ABC in the Ubermittelklasse or the Unterspitzenklase?" :-) ]
But one can _never_ generate a subcardioid pattern in the virtual X(Y) mic, starting out with a cardioid for M. The pattern of the virtual mic is always an intermediate of the two 'parent' patterns and can never be fatter than that of the starting M mic, no matter how much extra M gain applied. One needs to start out with something fatter for M than a subcardioid - e.g omni. In such a scenario, to achieve a subcardioid pattern of, say, V = 0.70 + 0.30.cos(theta), an M:S ratio of 2.33 is needed (i.e. omni M level is 7.36dB higher than the Fig-8 S). The included angle of this XY virtual pair is - no surprises here - 180 deg. i.e back to back subcardioids.
Some folks describe MS as being "more flexible" than XY. Not quite true, for the width can always be readjusted by the additional matrix step:
XY -> MS -> M'S' -> X'Y'. I guess you could say that XY is not less-flexible, merely longer-winded...like this post. :-)