Rex likes pre-snap movement to disguise the rush. Sometimes I wonder if that results in the slowness of the snap, or merely gives the appearance of it. Either way, it's not my favorite!
And yes, this ties into what Dareus said in that one interview. They want him gumming up the middle. This, unfortunately, sounds similar to what Albery Haynesworth said in that piece he penned for the Players Tribune. "Don't leave the TItans, Jim Schwartz is a defensive genius," etc. Still think Dareus will continue to prove his worth, but I want to see Rex take a page out of Schwartz's book.