SUMMARY This is really surprising, since all other stamps are shown exactly as they are named/shown. There should be separate "final" and separate "expired" stamp.
A possibly relevant merge request was started @ https://invent.kde.org/graphics/okular/-/merge_requests/467
Git commit 6b9a15fb1ad017517ce7abb66dba6be9105b1e6a by Albert Astals Cid. Committed on 29/08/2021 at 21:54. Pushed by aacid into branch 'release/21.08'. Stamps: Fix final showing the expired stamp M +1 -1 part/annotationwidgets.cpp https://invent.kde.org/graphics/okular/commit/6b9a15fb1ad017517ce7abb66dba6be9105b1e6a