The intent of Requires-Python is to require a minimum language version, and the language doesn’t come with prereleases. (It doesn’t even come with micro versions, but we’ve argued about that before.)
Requires-Python shouldn’t be used to try and select a particular CPython version. In practice the version numbers align, but in truth that’s coincidence (and in some ways it’s forced by the people who (incorrectly) insist that it’s truth).