He's not an expert, but he usually does good digging and has records on a lot of drafts going back quite a way.
So when he writes that those 40 times are kinda pedestrian for the safety position in the first round, I take it seriously. However, as I think someone posted before, Ed Reed's 40 time wasn't fabulous either. So I am open to other opinions.
Bob doesn't report out all his data (see Bigger/Stronger/Tougher) so its not a lock by any means.