Maybe "version freeze" or "feature freeze" is a better term. The sudo bug was fixed in version 1.8.28, but Ubuntu LTS didn't upgrade to the new version. They're still on 1.8.21p2 from 2017, but with the bugfix and other Debian and Ubuntu patches applied, resulting in a bizarre package version of "1.8.21p2-3ubuntu1.1".
Which with something relatively small and stable like sudo, is one thing. For big projects on rapid release cycles, like GNOME, it's got a much bigger impact.
Though I do see that Ubuntu does keep updating Firefox and Chromium to the latest versions in LTS, because they're so big and change so fast that backporting fixes has become practically impossible. That looks like a very rare exception to the rule; your typical Python library won't be getting that treatment.
Which with something relatively small and stable like sudo, is one thing. For big projects on rapid release cycles, like GNOME, it's got a much bigger impact.
Though I do see that Ubuntu does keep updating Firefox and Chromium to the latest versions in LTS, because they're so big and change so fast that backporting fixes has become practically impossible. That looks like a very rare exception to the rule; your typical Python library won't be getting that treatment.