The reason his legs were not as freaky as Platz, is because his upper body was also freaky, and better "balanced". Fukin huge arms, huge delts, good back for a man with a blocky structure, and thick pecs.
Those quads were surely the same size if not bigger than Platz at his peak.
Btw, I'm refering to De Mayo at his best, 30 or so yrs old. Not this vid at 21.