I would think so. There's an hour and a half block between the end of Nada Surf and the start of Deadmau5. This is pretty much the only time in the whole weekend where there is such a big gap in times. I'm guessing they need some extra time to get the whole stage setup ready to go. I wouldn't be surprised if Deadmau5's crew even did a little lobbying to allow for more setup time...thus leading to the late night stage.
I really think it's just to appease anybody who might be angry that the show's going past curfew. Probably noone will care if it actually goes past midnight, but shit would probably go down if certain people actually see it posted on the website.