I think the point really should be if you truely believe that you are going to be shot then, and only then, would I try anything like this. Another point to note is that the firearm must be at very close range, if not touching, in order to have any sort of chance.
We are taught a similar version at work, although ours commences with our hands up, but the the principle is much the same, although we favour direct assault rather than conveluted restraints.
I have to admit that I have never used this technique for real although I have trained it alive. I got shot nearly every time, to varying degrees.