The 4% body fat is actually what caught my attention. Frankly that could be what is inhibiting his strength. 4% is what bodybuilders get down to when they are at a competition and quite frankly is very close to the minimum that a human needs to survive. Im betting that the trainers get him up in the 7-10 range and with that he will gain a bunch of muscle. They do this and the overrated bench press numbers will go up, I guarantee.
I ran into the same thing when I tried to get my bodyfat as low as possible. I will never be 4% but I got down to 10% and my strength and endurance was fading because I wasn't getting enough calories to feed the muscle. You can talk about how much he works out but for you to be at 4% you are at a calorie deficit regardless if that comes from eating less or exercising more. At 4% the human body will use some muscle to survive.