The current *Interceptor* body armor is a LOT worse than the sleeveless/collarless M1968 flak vests we wore, about half the weight, though the Vietnam era tanker's helmet was fully enclosed and heavier than either the present issue Combat Vehicle Crewman's helmet or the Kevlar K-pot helmet that replaced the pound-and a half heavier M1 steel helmet in use since WWII. The newer armor is a lot better at stopping AK projectiles, of course: an AK round would go right through the front of a flak jacket, made for stopping shell fragments rather than bullets, and right out the second layer in back, too.
I doubt the crews inside the tanks are wearing full body armor, that makes it near-impossible to get out in a hurry. It's usually those detailed to groundpounder details or external security of their tanks so burdened. But tank crews may indeed be less used to operating in full armor outside their vehicles, and may be accounting for some, if not all, of the casualties.
