There's already a gif of it but two things:
1) Chalice dungeon boss only so most people have not experienced it.
2) The attack is less of a hitbox issue and more of a "ridiculous fast, full screen move with crazy tracking"
I'd consider it a hitbox issue if I was hit by thin air, which is what will happen if you dodge to the opposite side of the fist. Plesioth would be proud.