Mentzer did the same, 2 or 3 "warm-up" sets, then a "working" set to failure
Sure, you can't jump in to a max all-out set to failure with max poundage immediately, but the difference is, in the articles, they'd claim 1 or 2 warm-ups for first bodypart exercise, then the rest of sets for that bodypart would be 1 all-out set.
In reality, people witnessed them doing very traditional 3 or even 4 sets for 2 to 3 exercises per bodypart