Watch Mazi. He is routinely blown back to Linebacker depth.
And usually by a single offensive lineman.
You want your Nose to clog the gap and if possible, take up two blockers. This is how the backside Linebackers become unaccounted for and usually can free flow to the ball.
He's actually a negative 2 because since he is constantly getting knocked backwards, he muddies up the Linebacker's ability to get to his gap and/or make the play. His poor play allows teams to get 3 or more yards whenever they want. Parsons and Overshown are not great in run support either. The League has figured this out. The Cowboys coaching staff either won't or can't do anything about it. The Front Office doesn't want to admit they messed up.