[Graffur]

Just watched it on youtube. He doesn't use the fingerholes but I wouldn't expect all pros use them. The second hand just remains on the ball longer before the throw. My verdict: not that different

[retsibsi]

He uses the finger holes (you can see this in the front-on shots), but not the thumb hole.

[mulmen]

The holes are custom drilled to each bowler. If they weren’t being used why drill them?