These are the 2020 instructions for form SE from IRS

Changes to Schedule SE (Form 1040).
New Part III has been added to Schedule SE to allow self-employed persons
to figure a maximum amount of self-employment tax payments which may be
deferred. All maximum deferral amounts will be carried to Schedule 3
(Form 1040), and the total amount that you may elect to defer may be further reduced.

Seems like section 3 is for folks that want a deferral, and if so fill out section 3. Personally I am only going to fill it out if someone wants a deferral. 

I think some of you are making it more complicated than is necessary. Just my 2 cents