Yeah, I can see Shelton starting early mainly from just knowing the scheme and assignments that much better. I think physically he isn't what they want in a starting RG but you can;t discount simply knowing where to go and when. And if he is the presumed starter then Bruss will be given a lot of work in preseason with the 2nd OL which is exactly what he needs.
I'm with those that say Shelton starting week 1 doesn't mean he will be starting in week 7 or 8. And that's not a knock against him. He's a valuable part of this OL.