Using the PA Date of Birth dataset, we can see day by day mail returns incredibly correlated across the state, within large counties, across age groups. I'm not sure how you'd get these correlations without a central group drawing from voter records&filling out ballots en masse https://twitter.com/toad_spotted/status/1324896553459478536
Just another day of highly random social processes and individual freely-taken decisions producing perfect correlations at a day-by-day level precisely in a subset of large targeted counties in one swing state