Here's a good visual. You can see the two pieces of brass in the air right next to each other and the gun is flat. Also, you can see the distance to the target. Those were aimed shots and they hit.
This guy was using this technique or was he just double tapping? I'd bet he's VERY VERY good at double tapping.
I just don't see how removing your finger from the face of the trigger is any better when doing a DT.
I HAVE bumped my '74 and my AR with the 2-stage NM trigger and I HAVE experienced a failure to reset but in bumping, you're holding your finger still so you can't really practice this. That and the fact that bumping is silly anyway.