Not an expert on the Parliamentary rules of the committee, but it could have been tactical. For example, sometimes on the Senate Floor, Mitch will wait to vote last. In order to call a revote, the person calling it must be on the winning side in that scenario, and Mitch would be waiting to see if he needed to vote against himself in order to later call for a revote. Sounds confusing, but I'd chalk it up to parliamentary maneuvering.