Yes, that is exactly correct. The notification system for Kubuntu has been implemented for many releases now. Perhaps you just haven’t been waiting until the release team (which is the main Ubuntu release team) enables it. As I said before, the upgrade notification isn’t usually enabled for 1-2 weeks after the new release.
There have been more reports of the notification appearing in past releases from Kubuntu than your one report, so perhaps you just haven’t been waiting long enough and have assumed that it’s enabled on release day, which is not the case.
Additionally, per https://wiki.ubuntu.com/UpdateNotifier, the update notifier (granted, the Kubuntu version is different but it uses the same underlying code) checks for new releases only once every two weeks.
I’m glad your upgrade went smoothly, which is definitely feedback the release team needs before the officially enable the upgrade flag. Bear in mind, as stated in my previous paragraph, you might be waiting 1-2 weeks since it only checks that often. As I understand it, this is intentional as it enables a slower rollout as to not overload the servers and allows archive mirrors to populate properly.
IF, however, you DO find a bug, this would not be the place to file a bug. You’d want to open Konsole and type