CarolinaCane83 and umhurricano, the list is probably endless of HS TEs that went on to major success at other positions. It makes sense because the HS TE is usually a big kid who can run really well and is a very good athlete.
Whereas, you see some of these HS DTs and OL, and they're just big slobs who abuse small HS dudes in the trenches without giving much effort. Then, they get to the college level, and they're no longer going up against 5'10 240 pound OL named Howie Schwartz. Suddenly, the dudes they're battling are just as big as they are, so they can't rely on that inherent strength and blubber advantage to move guys around. That's what makes projecting DT and OL from HS to college such a difficult task.
Look at the bust rate of the 5 star HS DTs over the years if you need proof. Most of the great college DTs were dudes with mean streaks and athletic ability who put on significant size and strength at the collegiate level, and then wound up flourishing as juniors and seniors. Look at Nick Fairley. Non-factor until his final season at Auburn. Suh practically came out of nowhere too. He did NOTHING his first 2 or 3 years on campus at Nebraska.