Kactivitymanagerd remembers activity history despite "do not remember" in settings

I’m using Manjaro from architect, with unconfigured plasma-desktop.
I find the recent documents everywhere a bit off-putting, so I went to system settings -> workspace behaviour -> privacy
and set “Remember opened documents” to “Do not remember”.
I still get a recent documents list by right clicking most of my software, libreoffice writer etc. in my application menu. Clearing history empties everything, as does deleting the database where the recent documents seem to be held. The system setting, apparently, takes no effect.

I do not have my Plasma Activities set up to forget what files I’ve opened or what applications I’ve used, so I cannot comment on whether what you’re seeing is an actual bug or not. But either way, we are currently still on Plasma 5.19.5 in Manjaro Stable, and 5.20.x is already on its way down the pike ─ it won’t be too long anymore before it hits the Stable branch ─ which fixes many bugs that were in 5.19 and earlier.

However, I also do want to point out that LibreOffice is not a Qt-based application ─ LibreOffice is in a class all of its own ─ and that GTK-based applications do not honor KDE-/Plasma-specific settings. They have their own record of what documents you’ve opened in them.