Not that I've ever read about. However I do know a phase meter is standard tool in recording studios. It simply shows the balance between correlated in phase content compared to opposite phase content. Even today mono compatibility is important and the FM Sum signal travels farther than the stereo differenceing sub-carrier. So I'd say that's just about the opposite of what you, or I, would be hoping for.Is there any evidence that mixing "studios" are monitoring their stereo mixes with a surround sound decoder (maybe just a Hafler/DynaQuad setup)?