Thanks for noticing this.  The change in URLs was due to the introduction of the "new" python.org website a few years ago;  the canonical form of the URL for releases introduced after the move to the new web site is indeed  https://www.python.org/downloads/release/python-xyz/ so that should be the URL form used for current and future releases.  Another approach would be to add aliases on the web site to redirect from /releases/x.y.z to /release/python-xyz/ but, at this point, I don't think that's necessary.  A PR to fix the generated docs would be great.