I don't know why people believe this. If BA had the right TE he would definitely use him in the passing game as well. Sp if he had a Gronk I guarantee he would be used just as much.
There's really very little to back this up. Heath Miller had one Pro Bowl year with Arians as OC, and Arians has said he considered him the best TE in the NFL.
Gronkowski has 20+ more targets in three years where he's played 15 games or more than Miller in his top year.
My point is that teams he's been on haven't spent picks on top flight TEs because they're not in his plans to be used. Yes, in a world where for some reason he moves to another team and they have Gronkowski on the roster, I can see him using him, but I can't see him asking Keim to draft a guy that he'll drastically change his offense to feature.
Just like a team that employs a power running scheme is less likely to draft a Dalvin Cook or McCafferey.