"Specifically says that the 8915F is not to be used:"

It is written poorly; you are reading it backwards.

Remember the complexity, that 2020 disasters might have distributions in 2021 (FEMA can be a bit slow) that are New in 2021. Covid isn't New or carry-over in 2021. It had an expiration date in 2020.

"Beginning in 2021, additional alphabetical Forms 8915 (that is, Form 8915-G, Form 8915-H, etc.) will not be issued. The same Form 8915-F will be used for distributions for qualified 2020 disasters"

This part means, got the money in Tax Year 2021...but it's a 2020 disaster.

"(and qualified 2021 and later disasters, if enacted) and for each year of reporting of income and repayments of those distributions. The boxes you check in items A and B will help us determine the exact year of the form you are filing, and the year of the qualified disasters, qualified disaster distributions, and qualified distributions you are reporting."

Here is how you understand it: For Disasters years 2020 and later, for Tax years 2021 and later, use 8915-F. For instance, amending tax year 2020 with covid distribution or hurricane or fire (declared), means using 8915-E. For disaster year 2019, use 8915-D. For Disaster year 2021, for tax year 2021 and later, use 8915-F. Form 8915-E has one use: 2020 disaster distribution and 2020 tax year.

"When Should I Not Use a Form 8915-F?" <== written as Negative, but the rest is not

"Reporting coronavirus-related and other distributions for qualified 2020 disasters made or received in 2020. This form replaces Form 8915-E for tax years beginning after 2020." <== in that same paragraph, but written as Specific and positive to the action you need to take.

"Do not use a Form 8915-F to report qualified 2020 disaster distributions made in 2020 or qualified distributions received in 2020 for qualified 2020 disasters." <== specifically refers to 2020 distributions, reporting in 2021.

Covid is not a 2021 distribution. It's the reporting of the deferred income:

"Check the 2020 box in item B of your Form 8915-F if… and You are repaying, or have income from, a
coronavirus-related distribution or other qualified 2020 disaster distribution reported on Part I of 2020 Form 8915-E

Your form will be called Form 8915-F (2020 disasters)."