I don't think that's necessarily correct. It's not as if it's some kind of emotional handicap. It's a function of how the brain and neurological pathways work. When you know you need to control the gun enough to make a followup shot, regardless of grip, that probably slows you down. The more tasks or the more complex the task, the more it's likely to affect you.
Here's an interesting experiment, though: I bet this doesn't happen as much with unaimed (unsighted, threat focused, whatever) shooting. Because you're not really gauging the gun's alignment each tiny fraction of a second the mind doesn't have to accommodate for the next shot. Just a theory because I haven't tried it...