Absolutely a chop block, IMO. But what is more concerning is, the center judge was looking right at it and immediately flew his flag. I guess the head ref overruled him? Maybe he also had a good look, but they shouldn't have both been directly looking at the same thing. ANd if they were, I seriously doubt he had a better vantage point.
But also, that's how it goes. And it wasn't overly egregious.