It's not so much that it "generates" any "new" pass-rush, it's that it removes the main condition (offensive running threat/effective play-action, even on 3rd-and-relatively long) that stifled the pass rush capability we already have (which is not as weak as most people seem to think, IMHO).
With a 30-front that virtually eliminates any viable running threat on 3rd-and-long, pass-rushers don't lose whatever first-step advantage they might have by biting on play-action. LBs/safeties aren't late to coverage assignments by biting on play-action. More guys can be assigned exclusively to coverage without fear of getting beat by a run, thus leading to potentially more coverage-generated pressure (sacks or throwaways). And now, our pass rush might come from anywhere (like it once did when our defense was good) and the opposing QB has a less clear idea who is dropping into coverage or from what position.
IOW, we can go back to doing what was successful for us in 2001-2007.
I have to respectfully disagree with this assumption, especially if you are talking about 3rd and long defense. You cannot stop the run with 3 people. And you cannot take 3 people out of the pass defense and still expect to get to the QB (unless of course you are doing all kinds of fancy zone blitzes, which I don't think is what you're talking about). The only way you can stop both is by having players who are capable of doing both.











