Yes, it “works” (whatever you mean with that). When you unset DISPLAY on the CLI session, a GUI program there will not know where to open a window and will thus error.
I simply try to bring to your attention from the very beginning that doing anything with DISPLAY (or related) on the GUI session has no influence on what happens on the CLI session.
You still seem to think that setting or unsetting DISPLAY in a terminal inside the GUI session is “seen” by the CLI session. This is not the case.
I now tried four or five times, this is the last one. I seem unable to get the message forwarded. Sorry about that.