I just uninstalled XCOM2, as I finished playing it. When I reloaded GOG Galaxy, it showed that none of the games I previously had installed were there. They still show up as my having purchased them (thankfully!) but they are nowhere to be found onm the hard drive.

I checked the Games directory in my GOG Galaxy folder, and it was deleted.
Installing a new game recreates the Games directory.

Is this a problem with GOG, or with the XCOM2 uninstaller? I'd experiment with it again, but XCOM2 and expansions are about a 66 GB download...