Nah, that's not at all what I mean.
Mattingly's value comes from his versatility. He's a jumbo athlete and a good prospect. If he only wants to play TE, his value goes down. If he's not open to having the staff go "plug and play" until they find where he works best, his value goes down.
For example, Niklas was considered by some services as a great OT prospect... others as a DE... and instead he was open to playing OLB in his first year and then switching over to TE. KeiVarae Russel is another example of a kid who was a truly elite RB prospect but came in with a great attitude of "put me where you need me most" (he literally told the coaches that) and as such is a huge contributor.
If Mattingly is honestly as inclined as it has been reported that he wants to play TE then his value as a prospect drops considerably. He could could be great as a TE, but he also might never see the field at ND. If he was open to being a "glue" piece and play wherever he fits best then his value goes way up.
If there is one thing that is a necessity with undeveloped or flexible ATH prospects it's that they have an open mind, a very team-first attitude, and really want to be at the school. Otherwise the odds of them being a contributor go way down and the odds of a transfer go way up.