I can see that being a problem with the draw from any holster. In that oh crap death grip on the gun moment as soon as the gun cleared any holster your finger could go into the trigger guard just as easily.
Bronson
It's true to an extent, but the problem with the Serpa is that there is a mechanism for your trigger finger to actuate prior to firing. Worse yet, the motion is some what similar to a trigger pull, in that the finger has to be pressed in. The difference here is fine motor skills vs gross motor skills.
Having a conditioned response in the form of well practiced gross motor skills is as a matter of absolute fact something most adults count on to stay alive each and every day as they drive their cars. Most don't know racing techniques, but they get the idea of foot on the brake when they're about to hit something. It needs to be the very same way with carrying a gun. A set of conditioned gross motor skills.
Certain aspects of pistol defensive use can add fine motor skills, most notably reloading. A lot of people in combat situations end up needing like 10 seconds+ to do what could have been a 1.5 second mag swap because of fear and adrenalin. With some guns and some hand shapes, I would argue that the Serpa platform offers a similarly dangerous problem, except worse because it's possible that the first shot you fire might hit a high displacement vein in your leg, rather than maybe scoring 8 or 15 hits on your attackers.
I wish to again make it abundantly clear that I am not arguing with anyone who happily uses a Serpa. Certainly I didn't have these problems with Evil's XD45 in his serpa, at least not the trigger control issues and the way the gun draws. It is however a concern I now share with many others regarding the platform. Not really much else I can say on the matter that I haven't already brought up.