It's important to read this issue in light of the #TurdReich's concurrent assault ON THE POSTAL SERVICE, meaning that upholding the date restriction would risk disenfranchising voters who voted on time, but whom a crippled, underfunded, and Trumpist-led federal agency--for reasons entirely OUTSIDE THE VOTER'S CONTROL--failed to or merely CHOSE NOT TO serve in a timely fashion.

https://www.nbcnews.com/politics/supreme-court/supreme-court-tackles-dispute-mail-ballots-ahead-november-elections-rcna263748

Supreme Court conservatives appear skeptical of mail-in ballots that arrive after Election Day

Supreme Court to hear arguments in a mail-in voting case, weighing whether states can count ballots that arrive after Election Day.

NBC News