No one knows what a natural bodybuilder "looks" like.
I've read hundreds of these discussions about who is on and who is natural and all of that bullshit, and here is what I think.
1. How do you define natural?
I don't even know what natural means anymore. Back years ago, guys took pro-hormones, which were INDEED legit oral steroids. Yet because you could buy them over the counter, they claimed they were still natural.
So those guys claimed natural status (and you know who you are) yet it's obvious they were not "natural".
There were several guys that went into retirement or quit competing after these products came off the shelves. Why? Because they couldn't compete at the same level (and no, I'm not naming names but some guys are outing themselves slowly now).
Clen? Not natural. T3 or T4? Not natural. Is taking ephedrine natural? Some people say natural is defined by the organization in which you compete, and I personally think that's bullshit. To me natural means food, training, and sleep. That's it. Nothing else. Nothing that spares lean tissue, speeds fat loss, or dries you out that you can't do with food, cardio, and training.
2. Height and weight with leanness
I do believe there is a correlation here. My belief is, for the NORM, there are some height to weight to leanness ratios that generally cannot be breached naturally by the majority of human bodies. I am being careful in my wording here because there will always be an exception to that rule. But most guys that are 5'8" are not going to be able to walk onto a bodybuilding stage at 220+ natural. In fact, I feel pretty safe in saying no one could. And to get back to point #1, how would you ever REALLY know? People beat drug tests everyday.
Think of it this way. Arnold was pretty gifted genetically. And he competed at around 230-235 pounds at 6'1". And Arnold was obviously not natural. So if a genetically gifted bodybuilder can use, and compete at 230 at 6'1" are you really willing to believe that a natural guy could step onstage shredded, shorter than Arnold and almost as heavy? I have trouble digesting that.
3. "he's been lifting for X amount of years and trains hard"
I had this conversation with a really smart dude the other day. And we both agreed that muscle mass for a natural guy, is going to be pretty maxed out after about 8-10 years of REALLY intelligent training and dieting. There may be a morsel gained here and there after that, but the fact is, it won't be much. From there it's about a change in muscle maturity and density, but for the most part, the ratios are going to be pretty close to what can be done.
Just because a guy is dedicated and trains hard for 20 years doesn't mean he can naturally build a physique that can rival drug users that are also of similar genetic advantages. In other words, two guys with similar genetic muscle building ability, the guy that stays natural will never catch the guy that chooses to use. This should be obvious but I still see people arguing that if you just train really fucking hard for X number of years then "drug like" gains are possible. It really doesn't work that way. Trust me, I speak from experience.