This is very cool! I do worry it unbalances the half-elf and human, since part of the package there are the extra ability scores. Mountain dwarf also comes to mind. A half-elf or mountain dwarf gets 4 total ability score points, whereas most races get 3, and the non-variant human usually gets 6 total points. With this ruleset, these races would become slightly weaker. On the flip side, the variant human now has an extra point on top of the feat, making the non-variant human is even less appealing for play and adding to the variant human's power (which is already a top-tier race and needs no additional boost of this sort).
I think there is some work to do to rebalance any races who would not net 3 total points under the standard system. You get around this problem by allowing a player to choose standard OR this system, but I think it leaves a few of the races less potent, since some races have more racial ability scores than others in lieu of other racial traits. (Plus this makes the variant human even more unbalanced). I'd add an optional rule that this system replaces 3 points from the racial ability score increase, not the whole thing, as a possible fix. Maybe also stipulate something for variant human to stop them from being even more op.