It probably works because virtiofs connections look like local directories to Dolphin. Everything that is mounted as a file system falls under the ālocal filesā section in the Dolphin config. The āremote filesā part is only for things that you open using Dolphinās (KIO) URLs such as smb:// or cifs:// and the likes.
I may have been confused about when you said:
In that case were you using the Dolphin smb:// or cifs:// protocol to access the network drive directly, or did you mount the drive locally on some local path and then tried to access it?