Recent discussions on various MAGIC threads trending to sources saying ROR's testing has been unreliable for some time. Seems that there were discussions on whether to wait and open later until they fixed ROR issues, or just go ahead and open early. Fear of costly breakdowns with ROR and no real timetable for when it will become reliable....Of course, none of this is official, but they do have a few posters over there that usually have a pretty good handle on what's happening.
RotR testing unreliably does match up pretty well with what I've been reading as well. Jim Disney of Westcoaster did mention that they're taken aback by the phased opening, and while he couldn't go into specifics, it essentially boiled down to either opening early to help capacity and earn F&B/Merch sales...or delay the opening for the land significantly.