It's funny that the companies I've seen do this productively all have "other justifications" for doing so.

But effectively, yes, they're keeping high-performing older talent around so some hard won lessons rub off on the youngsters.

I always thought companies should spend more time broadly categorizing employee allocation. E.g. this year you're going to be 20% mentor, 20% strategic advice, 60% IC

Everyone wears multiple hats in a healthy company, and part of the ageism problem is that the only management-visible hat is "work produced."