It's similar to how an employer got to defer deposit of employment taxes they owe, and how some employers forced employees to defer FICA in 2020 that is now going to be collected and remitted in 2021, requiring those employers to issue corrected W2 for 2020. It's to bring parity to the SE.

https://www.irs.gov/newsroom/deferral-of-employment-tax-deposits-and-payments-through-december-31-20...