This is a continuation of bug #4160, but applicable to (at least) Ubuntu 13.04. From the comments:
"Once you've ever touched Gnome's display settings, it will try its damnedest to maintain that resolution, even in the face of external resizes like ours."
Also, somewhat strange behavour using xrandr - doing "xrandr -s <anything>" will
result in the session being resized to whatever the display size is set to in
Disabling xrandr plugin in the gnome settings daemon fixes the issue on gnome 3
browse to org -> gnome -> settings-daemon -> plugins > xrandr
and uncheck Active
At least on Fedora 36, there is no org.gnome.settings-daemon.plugins.xrandr setting.
Removing this file from the user's home directory will do the trick:
Note that this will also remove monitor preferences for local logins if the same home directory is used.