Just because everyone else says so. LOL. He has dominated some guys, and other guys he hasn't. When he has your number, you're toast. Speed, good moves, consistent pressure. Then he gets stonewalled against some other guys.
If it's only a matter of consistency, I think he can learn to be more consistent.
The concern would be that he takes advantage of weak linemen and gets stone by really good ones.
Also, the Penn State DL had a lot of stars on it, a lot of guys you needed to pay attention to, like Sutton and Durant.
OLs couldn't really key on any one player.
That being said, too much is made out of the lower production from Carter the prior year. He had Chop Robinson and another top senior in front of him.
So... is he a gamble? Yes. Are DEs notorious gambles this high? Yes. He's no more a gamble than Travon Walker or Kayvon Thibodeaux or Chase Young or Clelin Ferrell or Bradley Chubb or Solomon Thomas.
Only half these guys stayed with their draft teams.