I'll be honest, I find this math very confusing (as I am self taught using flakey internet resources similar to the one we're discussing :)). But my understand

I'll be honest, I find this math very confusing (as I am self taught using flakey internet resources similar to the one we're discussing :)). But my understanding is that there is a 2x factor somewhere that affects Shannon limit calculations. I think it might relate to the "negative frequency" mirrored half of the fourier transform at baseband. Or maybe I'm just doing the math wrong. In any case, the underlying concept is correct: a 2x2 or 3x3 MIMO radio can exceed the Shannon limit calculated for a single channel.