Platz trained upper body hard, I don't know how smart but that isn't thread title. He worked his ass off on everything. You can't help you insertions or genes... or how the judging panel in 1981 fucks you over.
There is a guy in my gym who kills himself training. Great form, lifts heavy as fuck, compound exercises and hammer machines - strong as an ox. Juices too. Great upper body. Legs of a child. I had better legs before I lifted (if you removed the fat)... Nothing the guy can do - he squats 4-5 plates a side for 10 slow reps full ROM, hits calves hard etc - nada. I do 3 exercises for legs and they are my best bodypart.
I think it should be in totality. Ronnie Coleman seems to enjoy training everything, like he was a workhorse for pain. Platz is known for his lower body workouts, he may have trained his upper body with intensity, but was it with the same intensity as his lower body? I don't think so, or it would have been talked about.
But, the two known for their intense workouts, and have won Mr. O's, Ronnie and Dorian, are also known for their torn muscles.
Honorable Mentions should go to Shawn Ray and Mike Francois. Both known for their work ethic---Shawn for using more weight and a fast pace, and Francios for using a hybrid bodybuilding-powerlifting training program.