I think GSP is natty, he seems like the type that naturally has a fast metabolism and just works out all the time his ENTIRE life.
I had a similar build to him when I was younger playing sports and kickboxing. I worked out all the time, and had a very active lifestyle.
If you keep it up all the time you don’t need roids to look like he does.
I’ve only taken off the shelf supplements and got up to 230ish ripped at my biggest. 245 not so ripped on a bulking kick when younger and 260 fat with that bulk still before deciding I wanted to be lighter again.
I think healthy 205 is perfect for my body type and isn’t all that hard to accomplish.
But to answer the op’s question I ha e some training partners that went the roid route, and they get a mental block off cycle, it’s like they need it to function at any kind of output level.
Almost like a Herion addict needs it to function.