Interesting design. Makes sense. I presume this isn't something you'd use on pristine or chromed fasteners - those "fingers" move a little to lock onto the flats, but by the same token, presumably might bite into the flats.
I'll bet they have their place - not sure I would skip traditional sockets and rely solely on these though. That makes me contemplate where they fit... E.g. If you have traditional 6pt for use most of the time, especially on good condition fasteners, then "extractor" sockets on the other (when you want the bolt out and don't care if you mangle it), it seems like these are somewhere in the middle.