Because there was aleady a schedule in place for tomorrow that didn't have to be altered. Bowie already had plans for their 7:15 time slot. Why change it? Why change anyone's time for tomorrow? There was no need for it. The only people that should really have to worry about altering anything for time and scheduling are the 7 bands moving to tomorrow from today.
Also, saying "there is little to no chance that AISD would have allowed Bowie to attend at their scheduled time" holds true to ANY band getting scheduled at 6:45, 7:00, or 7:15 tomorrow.
BOA should have kept it simple by leaving the current schedule in place and tacking today's bands on to the end of the current schedule. Simple. Easy. No one but today's bands have to change plans.