freelunch, watch out--you've got the curves there for the MK 4 axial cardioid, but your supercardioid curves are those of the MK 41 V, which is a side-addressed capsule. The curves aren't the same as the ones for the normal MK 41.
Your point is still evident, but not quite as clearly as it would be if you compared either two axial capsules or two radial capsules.
--best regards
[edited later to add:] Excellent, you fixed it.
As an even more clear-cut example, attached are polar diagrams for the three pattern settings of a Neumann U 87A, scanned from Catalog 140 (published in 1991). The 16 kHz graphs of all three patterns are almost identically narrow, but apart from that the figure-8 has essentially the same polar pattern at all frequencies, while the cardioid is distinctly wider on the bottom and narrower on the top than it is at, say, 1 kHz.
Problems in the pattern of an omnidirectional microphone generally show up at high frequencies. This one has that odd "propellor-shaped" response which large dual-diaphragm microphones so often show when synthesizing an omni pattern, plus at 90 degrees (and presumably 270 as well) it has a distinct 2 kHz bump. This is definitely not a nice, small pressure transducer.