The fact is that EVERY successful physique athlete trains a bodypart split
Yes but... So does pretty much every idiot in a commercial gym, and, 90% don't get very far very fast. If they get anywhere at all.
I still get the classic question, "back and chest on the same day?". I like to stir the pot and say, "back, chest, shoulders, arms, traps, forearms, and abs in the same day, thanks very much".
In seriousness, i'm not starting a debate. I feel much wiser now. I don't actually think the split matters, I think it's how you apply it.
There's a competing bodybuilder in my gym just now. It's quite good having him around. He stays freaky-lean year round. The guy has veins on his abs. Doesn't believe in allowing his bodyfat to creep beyond 10% in the off season.
I have a friend in the gym, few years younger than me and was always asking my advice. I gave him it through my own, admittedly biased lens - powerlift the big lifts, body build the rest, eat until it's a chore then eat some more. Worry about "detail" when something isn't growing or you start to get too soft/fat. I let him come in on my own training sessions for some free coaching, too, just to help him out.
Now he's being trained by the body builder (I actually nudged him towards this - training friends is not easy).
He's been put BACK on a bodypart split. Never worked before, why would it work now?
If it doesn't work now, I think it'll be for the same reason my approach never worked - consistency, discipline and really-hard-work (he only done what I told him when he trained with me, wouldn't do it on his own). What I told him to do put 4 stone on another friend in less than a year, who attacked it relentlessly.
Interesting anyway. This guy also likes to be innovative with machines - using chest press machines for rows and weird things like that. Anything that gives him a good mind-muscle-connection.