It’s the same issue as gender or race discrimination. There are often differences in means, but because within group differences are an order of magnitude larger than between group differences, from the perspective of any two individuals trying to understand each other, group membership gives you no meaningful information.
Knowing the averages will actually make you worse at assessment.
I've seen that in action. An older dev was an absolute burden on a hack day moving at a snail's pace. But for long term architecture he always had super valuable "oh I didn't think of that" things to say.
He was so awesome to have on the team, at the cost of sometimes having to watch him crawl toward a few lines of code. Not a hard choice in my opinion.
Of course I've seen the whole spectrum. Useless old people. Useless young people. It's best to simply be a meritocracy.
Knowing the averages will actually make you worse at assessment.