Doug, look into the following phenomenon called inter-limb interaction, sympathetic squeeze response, startle response, and loss of balance response. All of these involve the
involuntary contraction of the hand and finger muscles under
unplanned conditions. Read it, read it again, and then think how the way you choose to grip a revolver is just asking for an ND.
Now, looking at your pictures they remind me of something that I do that (AFAIK) I'll credit to Mas Ayoob, since he's the only person I've ever heard mention or write about it. He recommends the following when reholstering - with the revolver, one can place the firing hand thumb up against the rear of the exposed hammer, which does the following - if, during the act of reholstering, the trigger gets caught on something and the hammer starts to move, you'll be recognizant of it due to the position of your finger. With the 1911, while reholstering with the hammer back and safety on - the firing hand thumb goes slighty over the top of the hammer, which has several advantages. One, it usually removes the pad of the hand from the beavertail safety, activating it. Two, if the trigger was to be pressed somehow, the thumb is holding back the hammer. Plus, of course, the manual safety and beavertail are on or activated. With a Glock, or other hidden hammer (striker) semi auto - one can place the thumb against the back of the slide which will keep the slide from going out of battery when holstering. This procedure also makes it easier (I find, and others too) to reholster past the 3 O'clock position in a canted holster. Some individual's anatomy (shoulders and such) make it difficult to attain that angle and doing the above makes it easier.
Of course,
All of this is accomplished with the trigger finger in the guard position (along the frame - straight or bent if you like that method), and
not in the trigger guard.
EricO