Last year, the Packers blocked Alex Van Pelt from interviewing for the Jags OC position. Think they would block him 2 years in a row?
Actually IMO, McVay is looking for somebody who can be OL/OC much like Bill Callahan was somewhat in Washington that way that person can focus on the running game, however, McVay will call the offensive plays.
Teams just don't grant permission like they used to and that is why a new Head Coach needs to plan for that, also I would keep trying sometimes if teams block a guy once, they usually won't do it several more times because they know that can effect someone in many ways.
IMO, what teams need to start doing is creating opening on staffs when high profile guys become available I sure wish Jeff Fisher had done that when the Titans fired Mike Munchak and now he's with the Steelers. For example Bill Callahan will be available come 2018, McVay better be ready to pounce and I don't care if he has a quality OL Coach on staff, bring him in as Offensive Consultant very much like the Colts did with Rod Chudzinski.