This was brought to my attention through a private support request. If the “Tags are visible only to the following groups” tag group option is selected, the tags can be used and seen by the group members, but the tags and tag group are not displayed on the tags page. I’ve tested this both with the tags listed by group site setting enabled and disabled.
With the tags listed by group setting enabled, here’s what I’m seeing. (Ignore the weird tag names, screenshots are from my test site):
Here’s the tags page for a staff user:
Here is the tags page for a member of my eurorack group:
Note that members of the group can see the tags on topics and search for the tags from the tags dropdown:
I’m unsure if not displaying the tag group on the tags page for group members who can see the tag is the expected behaviour or a bug.