I could believe a 12 pound weight gain from April to August . . . but an added 15 pounds from camp to now seems unreasonable and not really very healthy and could explain not wanting to place him in the field in more situations as he learns to get adjusted to a weight he's never played at.
I could see 265 at this point but agree that 275 seems a bit much. Players usually don't gain weight during the season, the only reason I think he may have gained anything is because of his limited workload