What if they didn't? By all accounts, most of the 4 am ballots were ripped open and tabulated post haste without any Republican poll watchers present. Once tabulated, there is no way to cull them out of the system again.
Pennsylvania could show up with 7 ballots in their hands and say "there you go, Justice Alito, that's all 7 late ballots," and no one would be the wiser.
The systems show what the numbers are before and after the dumps. The ComDems are playing with the wrong people now.