They talk about the extra ordinary provisions due to Covid. They go on to reference:

(“[T]he Election Code does not impose a signature-comparison requirement for mail-in and absentee ballots.”).

So their argument is basically: 'We don't have to validate signatures because we changed the law so we didn't have to.' (Me paraphrasing)

Correct me if I'm wrong, can't that requirement only be changed by an amendment to the State's constitution?