Of course, as always, it's a halfway meaningless stat on older devices which don't get all the cool features.
I was excited until I found out that all my original iPad minis didn't get that feature in their iOS9 update. Neither did they get Siri enhancements, transit directions or multi-windows, apparently, among who knows what else.
But... Apple will brag that it's the "faster adopted update ever" anyway. Well, yeah, we were all figuring anythnig would be better than iOS 8. Unfortunately, it didn't even fix the Safari reload problem.