Engerek01: There is no difference. In one case there is alteration in abilities based on race, in other case based on gender. No balancing is required to see the resemblance. Alteration is alteration, no matter positive or negative.
Actually, there is a critical difference, from a gameplay perspective. There are trade-offs based off race, in that there are both good and bad aspects of such races. The old gender rule has no such trade-offs; the effects of playing a female character, when they apply, are strictly negative.
Let's consider the case of a fighter (so that the strength difference matters), and consider elf as the non-human race to consider (because both ability score modifiers matter here). Let's further assume maximum stat rolls. (If we assume average stats, we end up with a bunch of +0 modifiers, in a rather large range of stats because AD&D.)
For race: If we opt to make our fighter an elf rather than a human, we get +1 DEX but -1 CON. This, in particular, means this fighter is 5% more likely to hit with ranged attacks (handy if you're using a bow, this stacks with the 5% accuracy from their race, making their ranged attacks 10% more likely to hit), but also means they miss out on, eventually, 9 hit points. (The HP loss isn't that big a deal, especially if you're playing with max HP rules, but it is still a drawback of the elf, counterbalanced by the 10% ranged accuracy boost (and 5% melee with certain weapons).) (This is based on the Baldur's Gate implementation of the race.)
For gender: If we make the human fighter female, and we are playing with 1e rules (not 2e, meaning this discussion doesn't actually apply to Baldur's Gate), then we are left with 18/50 rather than 18/00 STR. This means +1/+3 instead of +3/+6, meaning that our attacks are 10% less likely to hit and do 3 fewer points of damage. (In practice, the difference usually won't be that big, but it will still be there on 50% of rolls that allow exceptional strength.) What do we get in return for suffering this peanalty? Nothing! Which, of course, is why it isn't good game design. It is not good game design to have one choice be strictly worse than another, unless the worse choice is clearly meant as a challenge option (I'm thinking along the lines of the Shepherd in Ultima 4; the Ultima 4 Fighter, on the other hand, isn't good game design IMO), and if the female choice is meant to be the challenge option, that is clearly sexism.
Engerek01: Whether realism is desirable or not is not the concept of my argument. Some may like it, some may not. Some may find fun in it where you can't.
If you get rid of the notion of trying to be realistic, than there is no reason left to impose the rule. (Again, there is a reason this rule is only found in one edition and was dropped in 2e.)