I don't think I'd call it meaningless; this sets the new default for the many orgs who haven't set a mandate already, and it seems to indicate that exceptions will now be harder to get.
Fair point. I've wasted way too much time arguing about this in my org. The messaging is effectively that the "data" (which is never presented to anyone) indicates on-site is better, and if you disagree, feel free to go test the job market.