Mike, I was not trying to say anything about my studio....and I also fully agree that we don't know what this dude was thinking because we weren't there to ask him, and you are also right that he may not even know what he was doing. I was merely using years of experience dealing with hundreds of engineers (I am starting to get sick of the rental business) to make a guess as to why. I see it all the time, especially with guest engineers. They overlook some little button because they have so much else to do. 99% I see that and point it out to them because I know that they have overlooked it. A newbie however may notice it and think it is some "mysterious technique" and I could understand how that could happen.
As far as OH phasing goes, OH's will always have a fairly considerable amount of phasing with each other since they are recording sources that are not in the same location. This is assuming of course a spaced pair and not some coincident arrangement or XY etc... In reltaion to the snare mic itself, they will also always have phasae differences. Snare polraity can certainly provide some options as far as tone goes though, especially when using a bottom mic in conjunction. I would probably never think to reverse an overhead though because it would affect much more than just the snare. Reversing the snare though can certainly be really cool.