I think that will be a slight minority. Also, they'll probably start running topicals for the 11:30 during/after the 8 this week. All in all this is a smart move, which BTW the "official" schedule corroborates:
http://www.adultswim.com/videos/schedule
My on-screen guide does not, however, but I'm recording the 11:30 this week anyway because I feel the one on the AS website is more accurate.
If I took a wild guess as to "why now?" All I can think is SDCC and the fact that they want better ratings for JoJo Part 3 as compared to AOT S2.