Default filesystem access lacks access to SMB network shares

I was recently linked to the list of the default filesystem access for completely unrelated reasons:
- https://github.com/flathub/com.xnview.XnViewMP/blob/137b345ba3c74aad6b24c0dc79ff81c03d35928e/com.xnview.XnViewMP.yaml

And I noticed that is seems to lack access SMB network shares, which is something I noticed in practice several months ago.

For the time being, I've been using Flatseal to manually add the following permission after-the-fact:
- /run/user/1000/gvfs

...but that obviously assumes that the user is "1000" which may not always work on multi-user OS installations.