Please note that there was a problem the last time that the name normalisation rules were changed.
According to the discussion in Escaping versions for wheel, sdist, and .dist-info names, the main idea was that normalisation would happen for - into _, but I don’t think the conclusions of the initial discussion included .. It seems that the PR that was merged ended up accidentally increasing the scope of the changes. Of course I might be wrong, and I apologize if I that is the case.
As far as I understood, one of the main reasons for the change in the normalisation was that installers use the file name to infer version and normalised project name without requiring extra queries to the package index.
This logic does not justify replacing . with -, because the heuristic for extracting parts of the file name involve splitting the string on the - character.
Previously, the setuptools maintainers manifested preference for not mangling unnecessarily with file names. It is understandable the need for replacing the - character, but . seems unnecessary. Ideally we should leave the file name as close as possible to the name the user intended for the distribution package. Under the hood we can use normalisation for comparisons (or is there a major downside in doing that?).