Adding significant muscle mass by exercise alone is pretty tough at 47 years of age. That's when testosterone typically has begun to diminish.
On the money regarding the testosterone. He’s probably been getting a testo supplement, which would explain the “dog tit” pecs and redistribution of body fat away from the abdomen. Another trick: look at his arms and forearms to see if his vascularity has increased more than explained by his weight loss and his moderate-at-best weight training.