That makes sense to me if he's still enlisted in the Army Reserves. If he has TRICARE Reserve Select, he'd be medically covered in a way similar to most other insurance plans. He'd pay a yearly premium, deductible, and copays... and the military would pick up the rest, as long as he went to a networked TRICARE provider. (I used to work for TRICARE.)
He could also be treated on base, if he made an appointment and clinic space was available. But he wouldn't be treated by the VA unless he'd been discharged. I wouldn't think.