Prime age is meant to filter college kids and retirees which makes sense but it is likely hiding the minor crisis in hiring for college grads. But I agree it's not disastrous just a yellow flag. The 20 year bull market has minted a lot of millionaires amongst the upper middle class and a lot of them are retiring early.

The 20-24 year olds seem to be at roughly the same point as since the great recession. https://fred.stlouisfed.org/series/LNS11300036

Worth noting this is people who have a job, it includes the under-employed.

There's nothing wrong with retiring a few years early if you're comfortable doing so. I sorta did. On the other hand, I didn't really want to hang around too long after either.