per

xdg-autostart-generator ignores all autostart items with the key
X-GNOME-Autostart-Phase

and now that kde plasma supports systemd user sessions, we noticed that several autostart items are not running. One of them was xdg-user-dirs since it contains
X-GNOME-Autostart-Phase=Initialization

I'd argue that xdg-autostart-generator should not do this unconditionally, and take more care to do it only where it makes sense.