The BMI is irrelevant to our point, mate. It's the fat-free mass index that's relevant. That BMI is a poor indicator of healthy bodyweight for a physically active individual is not under debate. We know it's crap.
That a person's fat-free mass may not exceed a certain level is under debate.
However, for most of us, that is much more a goal than a limit. For example, me at 1.77m tall could attain a lean mass of 78kg. At a healthy but not lean 15% bodyfat, I'd be 92kg (smaller with Casey Butt's method accounting for frame size, but let me dream!) I'm 81kg now. Another 11kg, 8-10kg of which is lean mass - I'd be pretty damned solid, with nothing to be ashamed of in my size.
Most of us are so far below the natural limit that it's not a limit but a goal.
I do like and admire the Pole in a lot of ways. If we had to hate every well-known athlete because they're a drug abuser that wouldn't leave us many to admire. But though I do admire him in some ways, "achieving a natural physique" isn't one of them.