I found this drop pretty odd.
One theory I had is that Millennials didn't always have a camera pointed at them, while Gen Z always has one on them, recording their every action. This, of course, could lead to punishments from parents much easier because they'd always be caught, or, a stigma around them for what they do while on camera that always follows them from their time in high school to their first job even.
Another is the #MeToo movement. If males are, for the most part, always going to get the blame — while it's arguable that neither party is able to give consent — it would seem like there'd be a higher amount of males that abstain from drinking to not put themselves in that position, and without males drinking, females would follow suit as there would be no alcohol.