Contrary to popular belief, the Triceps do not diminish so fast with age. The Quads do.
As far as why his shoulders/delts are smaller?
Easy.
Delts are a tell-tale sign of AAS usage. They have the most receptor sites of any other muscle group (per capita) in the body. Why? Because they are so fucking dense. The delts, traps and neck.
When someone is juicing really heavily, the first areas that really stand up and take notice are the delts, traps and neck.
The Triceps can stay forever. So can the biceps. Yes, they will get smaller, but not anywhere near the rate of the diminishing quads and delts.
Calves are a completely different story.
You either have them or you don't. If you have them genetically, you're still gonna have them clean, although a bit smaller.
If you've never had them genetically, all the PED's in the world are NOT going to help the situation.
It is what it is...