I know FFMI. That's why I think Francis Ngannou is 100% a juicer.
About Jeff: Nope. Can't be that ripped with that full muscles. An average understanding of how the human body works, will explain to you why. When you cut to get lean (and you have to cut) your muscles will get flat and depleted, there's no solution to this, it's a human condition imposed to every person, may he workout or not, nutrition discipline or not, top genetics or not. Simply isn't gonna happen.
More so, he makes a living out of his body, makes money. If he makes money (a lot), he'll do anything in his reach to look even better, that includes using steroids who will send his potential sky rocketing. He'd be stupid if not.
It's not about being clean, or even fair play: it's called making money, being famous in the fitness industry.
And btw there are many juicers with average or below average physiques, so their FFMI is also in range.