I was joking, but if you want to be serious, nymphomania and frigidity are NOT extreme ends of a bell curve.
"Nymphomania" is a subjective judgment that a woman has too high of a sex drive. A man with multiple partners over time isn't subjected to as much social opprobrium as a woman. It's a cultural judgment, not a medical term.
"Frigidity" doesn't tell you anything about how often a woman has sex, only that she doesn't enjoy it.
For that matter, a woman you call a nymphomaniac may not actually enjoy it, she might do it a lot hoping that someone eventually will "untangle her tingle".
So many things men could learn if they'd ask questions rather than give lectures . . . .