I don't know about "scheme". Gus is not exactly great with QBs, and didn't he pass on Castellanos when he was at UCF?
The mobility MIGHT be a thing, I guess, but to me that is a better skill when you are INTENTIONALLY using the QB in the running game. I'm not so sure it's a great desperation-trait when the QB is flushed from the pocket. Case in point is that video, Castellanos was forced to the right (his throwing side) and still underthrew what coulda/woulda/shoulda been an easy 20 to 25-yard TD pass, as the WR was behind the DB by a couple of steps.