It's more than an inch. Average/ideal is 35"+. The 33" number seen around is really the bare minimum. It's a "you have to draw the line somewhere" type situation. For Rhule, maybe his line is at 33 1/2" or 34". I think there is more to playing LT than arm length, but it's obvious it's something the coaching staff cares about to some extent.
I'm pretty sure Grier operated almost exclusively from the shotgun in WVU air raid offense.
Whether he was considered a runner is irrelevant in my perspective with regard to their focus on his drop back.