Why did Republicans flip?

The President's biggest talking point these days is the Republicans' flip on the bi-partisan budget commission.  Now, I think this is a great talking point.  However, his talking points skip the fact that there are often major changes in a bill between its inception and the vote on its passage.  Lets look at the reasons for this "flip."

1.  Congressional votes on the proposals issued by the commission would be cast before new members of Congress elected in November are seated.  This would, unfortunately, allow disposed members to affect law that the voters will likely not want.

2.  No outside sources can be used to obtain estimates contrary to the finding of the commission.  WHAT!!!  Huge red flag.

3.  Limited chance for opposing views to be presented.  Meaning only the commissions findings would even be available for a vote.

Given these 3, I would rather think that the "flip" was the responsible thing to do.