If taking the whole population into account, with the assumption that the number of male and female are equal; then the AVERAGE number of sex partners between the sexes must be equal.
Unless you consider masterbation to be hetro sex than there must be one f for every m. And let’s say most women have 4 partners over their lifetime. There will be a couple that have 50 and they have to be averaged into the equation. Thus M and F must be equal. There cannot be hetro sex w/o a woman.
Yes, your point is true with your stipulations, but apparently the statisticians don’t make the same assumptions regarding the size of the m/f split in the population available for engaging. I did not. The m/f constant fixes the numerator, but not the denominator.