Right, Classic. McVay wants a certain type of player at each position.
He had to be browbeaten after his dream of assembling a light, fast, zone-blocking elder Shanahan-Elway era offensive line fizzled (you can't ask lightweights to pass-block bigger men all day) before he eventually went with a different concept for both blocking and personnel. Result: Avila and Dotson.
Dynasty, you're right, too. The Golden Corral analogy is a good one. Speaking figuratively he'd never try a bite of everything but would go back to a fravorite meal every time if forced to eat there. He'd rather hit the sushi bar, and once there, stuff himself on calamari before trying the tuna belly - and that only if they ran out of squid.
Same thing with running backs.For his fine-tuned system he wants a certain sized running back, (and God and McVay know why but I don't) equipped with a Swiss Army knife or Leatherman Tool skill set. Forget the sharp butcher knife and the meat cleaver. (I like knife analogies for running backs.)
Gurley was an exception, and as draft strategy goes, a pariah - a holdover from the Fischer era - and Fischer wanted another Eddie George
type.