I don't see anything alarming about that fit. I'm a big supporter of as little reverse pitch as possible, that nearly eliminates any need or instinct to grip, but you can also go too far the other direction. It really depends on your hand, whether or not you're double jointed, dry skin or moist skin, etc. I'm willing to bet that the reason you like your rotation better with the 5/16 rev, despite the slight squeeze is that once upon a time you were fit poorly with excess reverse in the thumb and developed a habit of throwing the ball with your whole hand. When most people grip, they grip through the entire swing and through the release. The gripping becomes part of how you throw the ball, and instead of letting the ball naturally rotate as it's coming off your hand, people will rotate the ball themselves. You're most likely more used to doing the rotating yourself. Some things should be fixed, and some should be worked with. As long as your release is clean and the slight squeeze isn't hindering or negatively affecting your shot or causing fit issues, I see no reason to make any drastic changes. In this case, I would just recommend going with what is the most comfortable for you.
