They typically add a good amount of weight in those. I went to Michigan's Football States this last year
Also even if he did weigh 330lbs at the beginning of the season it is quite common for guys to lose weight throughout the year as they focus on football and not weight training or caloric intake as much. He could have been as low as 300-310lbs by the end of the year.
He doesn't look sucked out around the neck, which would indicate a fair amount of weight being cut to get to our 285lb limit.
I remember going to a football game a few years back when Michigan had one of those kids who was trying to do both (Gaige Garcia). He was listed at ~220lbs or something and one of the guys I was there with said he wasn't anywhere near that. Said if he had wanted to wrestle 184lbs in two weeks he could, which would have put him around 190lbs.