To me, this sounds like a wash, If your players are picking only optimized choices, changing what's optimized will change what they pick to a different set of optimized choices, yes, but that's the only change. This rule won't change optimizers into non-optimizers.
But that was never the goal: the goals were to reduce race essentialism (and I really don't want to re-hash that here so let's just say it's a goal and move on), and to make more combinations "viable."
Viable is not optimized, but it's also not ignoring character effectiveness. It's a middle ground between the two ideas, where the player feels they need to hit certain standards for the character to be effective enough to be fun and/or not a drag on the rest of the game. The more flexibility you have at chargen with core stuff like ability scores, the more options become viable.
Which means for a subset of players, this will increase diversity of characters. For other subsets, it will not increase diversity, but it also won't decrease it.
The only thing you lose is the mechanical reinforcement of the idea that elves are more graceful than humans because they have slightly higher dex scores on average. This is a loss, so I hope they include other ways to represent elven grace in future editions.