In 2 of the 3 times I've tried quitting Medium 2.0 (both with alt-F4 and with the VR "quit app" interface), the "cute walking shapes" loading animation will come up, and just stay up for at least several minutes until I gave up and closed it in Task Manager.
When I closed by alt-F4, the VR view stayed inside Medium; when I closed it within VR, I was taken to my Home space, but everything was very laggy and choppy, and the Medium window was still open on my desktop.