it was a long time ago since we implemented it and I don’t remember the details why we did it this way. I wouldn’t exclude that there’s a bug somewhere there, however we never saw any issues with it in the Kopano backend and as far as I know with the other backends.
ContentParameters class saves some options of the requested folder (the ones in the $unsetdata array, but it might actually be anything as we’re making a heavy usage of magic getters and setters).
Unfortunately I don’t have any time in the foreseeable future to dive deep into it. If you’d be able to solve it, the contributions are always welcome.