I have also used a fair bit of patient but can't ever recall seeing a 2/3 zone used against me. Obviously we all agree 3/2 is the best defence but my (untested) thinking is that comparing the options:
M2M
Opponents SG playing at C taking outside shots against your C with atrocious OD.
2/3 Zone
Opponents SG playing at C taking outside shots against your PG and SG who are "working their asses off" to cover the outside and performing much worse than their normal wondrous levels. Maybe down to around as low as prolific to respectable effectiveness.
Occasionally with the M2M, though, you might have enough OD to prevent the ball from getting to the mismatch in a good shooting position in time, whereas in the 2-3 the passes get through much easier and if for some reason they don't, the guards will still have a much easier task should they choose to drive or shoot over the weakened defense.
I think it's an interesting idea at least, but I keep coming back to the crazy notion that against that type of player, you want to either make him miss more shots or make sure he can't get the ball, and the 2-3 says "Here, have the ball, and we won't bother defending you either."