The problems is the millennials aren't as focussed on privacy as the generations before. They're open to participating in targeted content whether it be ads, stories, offers, etc.
But this isn't to discredit privacy concerns at all. Google anonymizes its users so that individuals aren't identified. This is a better approach compared to other questionable "targeting methods".
I think it's overstated to say that millennials are properly perceiving the privacy issues in play and making a reasoned judgment to participate anyway. None of my friends (not millennials, but 20-somethings) really understand all the things Facebook allows themselves to do with your information via their ToS (and many of them are lawyers!) They just assume that it wouldn't be legal to do anything really egregious (which is how most people view most things, actually).
Furthermore, you can't point to a group consisting entirely of young people and just write off their behavior as "generational". A lot of youth behavior is simply driven by... youth. Youths are known to take greater risks even when fully informed of the potential consequences.
But this isn't to discredit privacy concerns at all. Google anonymizes its users so that individuals aren't identified. This is a better approach compared to other questionable "targeting methods".