That isn't a mistake, that is a delaying tactic. Barr isn't dumb, he knows what documents he didn't provide. He didn't provide them because he knew the court would order him to provide them, and give him several weeks to do so. Trump has no case here, and he knows it, but all he has to do is drag the case past Nov. 3.
On November 4, Trump can give a speech on the White House lawn about how much she deserved to be raped and it won't matter. But he can't have this case actually spill the beans before then.