I've often wondered if it isn't about positional fit with some of these guys. Over the years there have been quite a few of these DEs we miss on and they often seem to head to teams using a 4 man line where they still have a chance to play on the edge as a hand down DE with their body type and build as-is, where if they play for us, it's pretty certain they're going to be asked to add 20-30 pounds and play one of the 3 big-guy roles where the OLBs are the edge players <or> lose 10-20 pounds to be able to play an edge role.
Looking at the clemson depth chart, they've got a TON of DEs in the 260-270 range so he fits their prototype. Looking at the bama depth chart for DL, we only have one guy in the 260's (True freshman without the benefit of our programs yet) and one at 278 (played very minor role in only 4 games, none that were a contest, over 2 years) and all the meaningful contributors are 290+. All the meaningful edge guys are sub 245 (one is 260+, but a TF so I'd bet he morphs one way or the other).
So if clemson is projecting him as an edge DE, or just selling him that he'll have the chance to compete there versus being a DT, he could just feel he that's a better fit for him versus what we are likely telling him.