Why? All things are possible problems, including formatting rules.

Possible problems catches codes with bugs. I don't care about formatting rules because I use prettier.

Prettier doesn’t format everything, and anything it handles is disabled by eslint-config-prettier.

Yes but the categorization it is still useful for when I need to find a rule I need. For example, when I need to find a rule thats warns about unmemoized context value, I know it is a possible problem instead of a formatting issue, so in this case I only need to scan about 10 rules instead of 80 rules.

Suppose it is Friday, and the product would be released today, and you can only fix one of possible problems or formatting issue, which one will you choose?

Since formatting issues are autofixable, I can't conceive of when that would come up in the first place.

If we can automatically generate this information in the readme, I'd be happy to review a PR.