Changelog and Release Notes - Single source of truth?

I suggest a single source of truth to document changes. Currently:

1. CHANGELOG.md
2. GitHub Releases page

Wouldn't it make sense to avoid duplication? How about keeping GitHub Releases and discarding CHANGELOG.md? This would imply that:

• the contents of CHANGELOG.md are not appended to README.md any more, removing the need for a dynamic README while building sdist,
• and on the PyPI project page, changes would only be accessible through the existing Releases link - but that's what "all" projects do.

Are repository maintainers able to modify release notes GitHub Releases page after the fact? I am asking because it would allow to align this page with the contents of CHANGELOG.md and then get rid of CHANGELOG.md.