Zane is a proven liar just for that time he tried to pass a blatantly photshopped pic of himself off as real. Remember that?
I think it was in the patent for Ciba dbol that they used a process to remove the selenium(? I can't recall exactly right now) that apparently other makers didn't/don't and maybe that was the reason old timers who used ciba dbol said it worked way better. I knew a guy who first thought maybe he just didn't respond like he used to just due to age/acclimation of some kind, but it could be that was a difference that made a difference.
As far as what the Arnold era guys used, no one is really ever going to know. There's the story that Arnold started taking dbol when he was 15. Then there's Sergio and his "candy jar" where he just took "handfuls" of dbol when he felt like it. Stories of Platz taking so much dbol "his kidneys hurt". Could just be completely made up stories. Arnold really doesn't strike me as the Yates type to keep a written log of what he's doing.