You have to put into perspective though that nearly all of the guys ahead of him a significantly bigger, many of them fullbacks. And like HuskerShark said, bench is pretty irrelevant anyway. It's basically looking to see whether a guy had a great work ethic in college as far as getting in the weight room. A low score in the BP is much more noteworthy than a high score. Take a look at DJ Fluker. He only managed 21 reps, the same as Burkhead, at 339 lbs!
Did you actually check or are you just guessing?
Rex - 214 lbs - 21 reps
Knile Davis 227 lbs - 31 reps
Mike James - 223 lbs - 28 reps
Christine Michael - 220 lbs - 27 reps
Zac Stacy - 216 lbs - 27 reps
Michael Ford - 210 lbs - 25 reps
DJ Harper - 211 lbs - 23 reps
George Winn - 218 lbs - 22 reps
Perhaps 14 lbs to Davis is "significantly bigger" than Rex to you but that's someone who Rex would directly compete with. And none of the others are more than nine lbs heavier - some are lighter.
I'm not trying to run Rex down. Look at my post: "For Rex, average is struggling" I knew he would be low in the 40 but expected him to be near the top in most everything else. With his work ethic, I was surprised he didn't test a little better in the bench press because he seems pretty strong and I'm sure he knows the way to the weight room. It's not that big of a deal, just surprising to me.