You are correct, but there is more to it than that. At one time I was a serious lifter-- and I did half a dozen cycles. Even though I haven't worked out serious

You are correct, but there is more to it than that. At one time I was a serious lifter-- and I did half a dozen cycles. Even though I haven't worked out seriously in 3 or 4 years (illness, childcare, divorce) my body shape is permanently altered, as are my overall strength levels. So, when I was entertaining trying to be a bodybuilder, I had two problem areas. Chest and arms. Also, I should mention that my trainer at the time was an IFBB judge, and has his pro card. I really, really dived into this. My chest got big from gear and stayed that way, and I kept most of my strength, even when I don't work out. The reason I can't be a bodybuilder is-- I can't get my biceps to grow, even on the most aggressive steroids they grow mildly and shrink back to crap the moment I'm not killing myself. My point is, bodies are weird. They're an indignity frankly. Anecdotally, I have evidence your supposition is correct and incorrect. It's mostly down to genetics.