I think I read that the rules are a bit vague saying something like “release the handle”. And don’t clarify if that explicitly meant the handle is the last /only thing you can touch.

The rules are clear that they can’t touch the stone after it starts to cross the hog line. Which I’ve seen a video of him still touching the granite when the stone has clearly started to cross the line and that’s unambiguously against the rules, regardless of if the touch influenced the stone’s movement.

Edit: I just read the link on the comment above yours. They quote the exact rule in question, and clarify that their official interpretation is that it means touching the granite is against the rules.