Hmmm ok, that sounds about right in general. 

I suspect he dudes looking at this weren't considering general eq conditions like that, just intertemporal savings for a young person growing into retirement 

I'm just trying to figure out who has the shares that these younger folks are "supposed" to have and what the error is that's leading them to hold the shares.

The easiest answer, that I think you've written about, is that Boomers aren't spending enough. The win-win, then, is Boomers get more utility from consumption by selling their stonks and millennials get the stonks they should have.