Although Aphrodite's hand obscures the pubic area, we can see behind the hand, and see that this hugely influential, game-changing sculpture had Barbie crotch.
1. The Aphrodite at the Museo Nazionale Romano, from a different angle
2. Roman copy of Aphrodite of Knidos at Glyptothek, Munich.
The original Aphrodite of Knidos has been lost, so we can't say for sure if it was Praxiteles's intention to give Aphrodite a Barbie crotch as a stylistic choice. It may be that he didn't bother because it was under a hand anyway. Or because the sculpture was displayed painted, it's entirely possible that the pudendal cleft was painted on.
There wouldn't have been pubic hair on the sculpture, because the ancient Greeks absolutely hated body hair in art, on all genders.