Pretty unusual though. They could just as easily have waited for Beta 4. Unless this was solely to get the 7/7+ on the same track and develop a week's worth of user data from the entire fleet.
Totally agree with you on this. Even the release hour suggest it's something that was not ready a long time ago as most betas usually are. They probably want to keep everything in line to mitigate the confusion that may arise from this.
They usually are ahead internally. so they may have found something on 7/7+ internally. Speculation