It's not about delay, it's about what happens when there are hundreds of thousands of fewer ballots than were counted. If they force the auditors to move the ballots then the board of supervisors are also no longer in control of the ballots. When the count comes up short because of all the destroyed ballots, they can try to claim the auditors lost them.

If the ballots never leave the building they are currently in, the board will have no way to shift the blame.