Auto compress not doing anything (GUI, Windows)

[Lieferschein]

Maybe I have the whole thing wrong, but when checking "Auto compress" I still can't post a folder (error "You can post folders without compression"). So I still have to manually check compression (on the bottom of the GUI) AND still have to check "generate par2" as well.
Even when posting single files, PARs are not created automatically.

Is this an error or am I using it wrong?