The bench press and strength test means nothing in terms of football skill, but in the case of either huge improvement or huge numbers like 500lbs shows that he has an incredible work ethic.
I think that's true to an extent. There's also the question of natural talent and body-type. Not everyone will be able to bench 500 lbs, no matter how hard they work. In the same way, not everyone will be able to run a 4.3 40. But yeah, you'd have to be a natural freak to lift 500 without hitting the weights pretty damn hard.
Having said that, I always thought that the bench was a pretty useless measure of how well someone plays ball. You rarely, if ever, replicate a bench press when playing football. I think it's a good measure of overall upper body strength but football is about using the strength you have in the right way and being explosive.