The contact doesn't happen on the 29. It happens right around the 30. The Steelers blocker has both his legs behind the 30 and the Browns defender is right on the other side of that marker. The contact literally happens exactly at the 30.
The issue with OPI on picks is that it is called often in an inconsistent way but in this particular case there was nothing blatantly wrong. If you seriously want to fight about a few inches +/- then lets maybe have a conversation about how footballs are spotted after each play because that has a substantially bigger impact on everything than something like this here.