Why do you keep referring to top bodybuilders? How do they apply to some random kid you know nothing about (OP, I know youve stated you arent going to use at 18)? Furthermore, all bodybuilders national level amateurs and better (and plenty of guys only doing amateur regional shows) are on AAS all year round. If a kid wants to start at 18 and go for the big time he may as well be prepared to stay on (blast and cruise) for the next 20 years.
And yes we do know what ferigno looked like as a teen, there are pictures. We know what cutler and branch looked like as well. Same for ronnie. Youre still missing my point about this. 99.9% of people dont have the genetics to make money in bodybuilding. That alone should be enough to get 100% of teenagers to not use.
Additionally, an 18 year old looking to turn pro within ten years is not missing out on anything by training without AAS for 2 years or so. If he has the genetics to go pro he'll grow like a weed and in perfect proportion.
Why do you keep asking if there is proof that an 18 yaer old man's endocrine system is not as developed as it will be at 28? Do you not understand how puberty works? I feel like I'm talking to someone with no experience at all and that this is a huge waste of time. It's like youre asking me to prove that the sky is blue. There are studies showing that some men finish puberty after their 21st birthday, go find them.