I have a UPnP media server (my PVR box) and on MacOS, any attempt to open a 'folder' will both open that folder, and automatically start playing the first item in that folder. I'm double-clicking a folder like recording\Frasier and it plays an episode from that location, or opening "recordings" and it plays whatever it sees at the top level.
It DOES open the folder too but then unless I hit stop within a second, it starts playing the content before I can find the actual file I want.
Under the folder structure it seems to show each 'series link' as a single item e.g. "Frasier (38)" so 'expand all' does nothing. Maybe they are being exposed as playlists or something by the server, it's hard to know what might be a VLC issue and what a server issue!