C´mon. Besides that I don´t say that this is the true reason for the BBs doing it (as I´m sure it is not), it´s a well known fact among all software and even product managers that the only way to REALLY make something work is to give it to the customer and see how he gets it broke.
You can do a 99% reliability test, but there´s so many different options, configurations, and even "stupid" behaviour possibilities in even using an HOURGLASS that even if you think you have everthing covered the next day Neil Armstrong calls and tells you that for some strange and unexplainable reason it doesn´t work ...
Going live in an core part of any system with a changed something is always a risk, and if you get a "larger" beta test without the chance of anything breaking apart, you take it. And it´s only fair to the users - everybody gets a glimpse of what´s going to happen and can adjust.
This time, it´s even more fair, as the supporters don´t get a key advantage. Whatever you do, it´s wrong anyways...
Zwei Dinge sind unendlich, die Dummheit und das All...