If that were true, every pro would look like Ronnie. All pros are doing the same thing, but they all don't look the same. Genetics and work ethic are just as important as diet and drugs. You need to face facts swimmer boy.
The IFBB pros are not using the same controls and vairables with their drug regimens or training or nutrition.
To have a REALLY accurate study, one would need to take a large segment using the same controls and vairables.
For instance, to figure out the effectiveness of a certain supplment, you would want to take as many people as you can, break them into individualized groups that share the same qualities, such as muscle mass and height etc. and then control all vairables such as diet,training and nutrition and duration.
It wont matter if someone is a Bodybuilder or not since the genetics are the same. Humans do not vary much at all.