I stand by my point, that is a yellow.
I agree, he didn't hit him with the studs but the outside of the foot. Was very surprised Sabitzer thought it was a red as well and think that might have influenced the referee decision/possible VAR intervention. It's very nice to see a pro displaying self-reflection but maybe he maybe even took it a bit too far in this case. In my opinion the VAR should have insisted on a review of the situation.