If you squeeze the grip there could be a tendency to torque the bow upon release and thereby creating inaccuracy. If you did it the same way every single time it is something you could work through. However, it's rare that a person squeezes the exact same way every time at the exact same time. Especially when you are shooting at game at an odd angle or even with a good stance. To understand this just hold your bow out with a firm grip and then squeeze the bow and watch how it will turn and/or twist in your hand.

This grip below was shown to me by a gentleman at the local range and is also posted on the Matthews forum website and really helped me become consistent with my release.