Which is ridiculous, no? Football consists of far more short bursts than 40 yard straight line sprints, which I suppose is why he is putting it off. Far too much attention is paid to the 40 than skills that can actually translate to the field. Be that as it may, it appears shoulders have far more to do with running than meets the eye.
I was watching the defensive linemen run the 40 yesterday and it was almost embarrassing. First of all they are all in a three point sprinter's stances, with their hand about 3 inches from their front foot. Some of their bellies forced them into pretty uncomfortable looking positions (to be fair, they have been doing that for about 15 years), but when was the last time you saw a DT in this sort of stance in a real game? For some of these guys, you can time the 40 with a sun dial. Sure, most are in decent shape, but they were laboring by the time they reached 25 yards. Finally, when was the last time you saw a defensive-run-stopping-tackle catch a running back (or even a Tight End) 30 yards down the field?
I'm sure scouts can glean a little bit of info out of it, but my guess is it would be far more beneficial tocut the length down to 20-25 yards for linemen.