I use pinch in/out in virtually every program all day long. The only time it would be off is when I'm away from my desk.
Crazy thing is that I'm not in Finder when this happens 2/3 of the time. It's as if the pinch open gesture in an active window "bleeds through" to Finder to echo the gesture. I don't see the huge icons until closing the program windows (or on the periphery, should there be a sliver of desktop visible at the edge of the monitor).
As for whether or not I like BTT otherwise....? No clue. The only thing I got it for was to rectify this crazy desktop icon problem.
As an update:
Spent about 15 minutes on the phone with two AppleCare techs, both of which tried to tell me that while I was typing in one program I must have accidentally clicked on Finder, which brought it to the forefront, then I pinched out, then the icons blew up, then I clicked on the program window again and did all this so fast I didn't see Finder become the active program.
Seriously?
They also tried to tell me no one has ever complained of this before (again, insisting it's user error), to which I responded that they may want to peruse the Apple Support forum since there are others there (and here) with the same issue.
Finally asked the second guy what would happen if we simply trashed the Finder .plist and rebooted (a suggestion made by another AppleCare tech, according to a poster in their Support forum). Gave that a shot, and will see how it plays out over the next couple of days. Fingers crossed.
First time I've been frustrated by Apple Support. Weird experience.