There is no way the group and especially Hemi who's a choreographer would believe that they are performing at 11 PM in the amphitheater, on every festival evening there is only one show in the amphitheater between 9 PM and 11:30 PM (roughly). If there were the ones performing in the amphitheater there show would have started at 9 PM.
Thus it is also doubtful that they would fall for the trick of starting at 9 PM at a different venue because the festival never schedules shows and dancing sessions between 8:30 PM and 11:30 PM, to attract a big audience to the main show in the amphitheater. Even if that would be done for spite, Hemi, who's a choreographer and has other groups performing, would know better.