I've not fallen becasue of clipless. But I feel I had an advantage. At the time I started cycling with clipless the skiis I used had a binding system where to release you 'kicked' the heel out. Pretty much the same action as SPD pedals, which is what I went wit. So it was an action I was used to. I could even claim net negative falls as I have caught at least one other rider who failed to unclip. (unclip right, lean left).

I've also seen at least one rider who went from clips and straps to clipless. For those I'd expect no falls, you are going from a much more difficult process to an easier one if you are making that transition.