Good job with core muscles. Magnificent job. The front looks tight.
His back on the other hand... It just looks flat. Trained back should be thicker. Muscles are pretty small and toned. There are big muscles in the back too. And where is his rear delts? There are just holes where they should be. You really need to spice up his upper body workouts. Needs more buff.
What they mean with "calf muscle bigger than the roman empire" is that they are massive compared to it's thighs. Usually thighs are bigger/thicker than calves. IMO calves are too "deep" (as in expand a bit too much back while still being really thin when viewed from the front) But I won't argue with that since we can't see the thighs properly.
And of course you are making your own creation, feel free to take some freedoms with the anatomy. But don't overdo it.
Looking real neato.