Was Sullivan as great as Joe Louis and Muhammad Ali ?

All he is talking about is turning the punch over; you turn every punch so that those two large knuckles land. I don't think that that poster actually understood what he was saying because turning your hand like that is going to lead to a ton of hand and wrist injuries. One of the most common injuries in modern BK boxing is breaking the outer two knuckles on the hand by turning the fist too far and landing on those knuckles; even if they don't break, pushing them up towards your elbow really hurts at first.
I am 100% open to the idea that John L had skill far beyond modern BK guys; it was the only show in town at that time and people then were generally stronger. Punching like that would require very very strong hands and wrists but I don't see it. At very close range, maybe, but, at distance there is too much that you can't control.