That's EOL for source releases from python.org. If you get the binary installers, or Conda builds, python-build-standalone, or a distro package, you'll get different dates -- and also different *kinds* of support.
IMO, the devguide chart is aimed at core devs, to see when to backport what.
Perhaps we need user-facing docs... but then we'd probably need to define what we promise as “support”.