I wish I could explain this a little better than I am going to attempt, but will probably cause more confusion.
I was at FF. Saw the BD placement, the Petzl and Grivel placements. They had two huge blocks of ice, maybe four feet by three feet by 18 inches deep (this is a rough estimate on my part).
The ice was crystal clear. You could see all the way through, front-to-back, side-to-side.
The BD screw was being placed. You could see the ice almost expoding the deeper the screw went in. It almost looked like an instant spider web.
The Petzl was easiest to place, but there was still distortion of ice upon placement, but not nearly as much as the BD, maybe 80-90 percent less.
The Grivel went in. There were no fissures, or "explosions" or spider webs created - just a very nice, clean placement. No distortion of the inner ice at all.
Perhaps some the folks at FF could be a little more artful than I in explaining this. I wouldn't have believed it if I didn't see it. Damndest thing I'd ever seen.
I hope I am somewhat clear.