JACK-was watching my older son take some slow motion dry swings and looks like a release of the hands before impact.do you hold the tourque you ceated at the top all the way through impact?
From my first reading of your post, I thought you were saying your son might be releasing his top hand from the bat before contact. I noted in a closer reading that you used the term "release of the hands before impact." These involve two very different batting principles.
I have no problem with a batter releasing his top-hand from the bat after contact. After contact, the ball has left the bat and therefore releasing the top-hand, or keeping both hands on, makes no difference in how hard the ball is hit. However, if you were saying that during his 'dry swings', it appeared he released his top-hand prior to contact, that would be a problem. -- I doubt this is the case with your son's game swing. I think a video would show his top-hand still on the bat at contact.
How let us address the "releasing of the hands" controversy. This term stems from the linear "Crack of the Whip" theory where energy is supposedly stored in the bat just waiting to be released. This linear theory basically states that this stored energy comes from the batter's forward weight-shift and linear extension of the knob.
The batter is told that this stored energy causes the bat-head to fly around like the "crack-of-a whip" when the hands slow at full extension. The batter is warned not to release this energy too soon. Some batting authorities say; "Don't squeeze the trigger to soon." They believe the bat-head should trail behind the hands and not be 'released' until the hands near full extension.
This is not the mechanics we see in high level swings. The best hitters are constantly applying forces (torque and the pendulum effect of a CHP) to accelerate the bat-head around the swing plane right from initiation. Take a look at the bat-head's acceleration from the over-head views of the swings below and draw your own conclusions.
Demo - "Whip Effect" vs CHP (Circular-Hand-Path)
PLT/THT -- Overhead View
Rose - Keys to CHP