I think they are trying to keep the Nation machine off of him - now, I think it is more likely he goes to Pawtucket to replace Peralta. But remember Benintendi's callup was a surprise - we saw how he had demolished High A and AA and wondered, but the FO left no hints at a pre-September callup coming.
As i have noted before - would I be surprised if Devers joined the team next weekend? No. The Red Sox could dream on Lin, Holt (when he returns) and whatever providing a warm body there ... but no other option inside (or maybe outside) the organization has the same sort of ceiling.