The tags do show up in the NFO files though, and it works as expected (hiding the media with the "nope" tag) for about a week, until the tag is removed by Jellyfin, presumably during a refresh of the media.
Here is the contents of a .nfo file that still has the tag:
https://pastebin.com/VeTKdn9Y
After a refresh, the "nope" is removed from the tags line, and the lockdata line is no longer there.
Here is the contents of a .nfo file that still has the tag:
https://pastebin.com/VeTKdn9Y
After a refresh, the "nope" is removed from the tags line, and the lockdata line is no longer there.