If one cants a bow, then thats a fair grip. Your grip no matter if canted or vertical should be just like you holding your arm out naturally, just like he has it.

I have no problem with a canted grip like he has it. Its the way I shoot my straight grip longbow.

And yes, if you shoot feathers and fingers, you can cant a compound and shoot like he is doing. You have to get the arrow pushed away from the riser to be more centershot which you can do iwth a flipper and plunger or bowdoodle made for fingers.