Thanks very much again, tj. I think you're pretty much correct in every regard but our steps differ slightly causing slightly different results.
I have been entirely unable to reproduce what you are seeing with the Artist field being populated, no matter what I tried with filename structure.
I suspect it's due to the pattern you used. The inference pattern seems to be <Artist> - <Title>, not <Artist> - <Album> - <Track#> <Title>. When the pattern isn't matched, the entire filename seems to be treated as Title.
Try using the wrong pattern (e.g. no whitespace), then open MusicBee to make sure Artist is empty. Then close and rename them using the correct pattern (<Artist> - <Title>) and re-open MusicBee. The Artist tag should get (pseudo-)populated.
I think another difference in our steps is you're using the inbuilt Computer Node to browse and edit files whereas I just rename them in File Explorer like a troglodyte.
I've also just updated to the latest build (was on 3.5.8447 which was one version behind) and the behavior is unchanged.
Where on earth are you getting all these files with no title or artist tags?
YouTube using yt-dlp. I had an error in my config causing it to strip all metadata except one field (Comment, populated with the URL).
I can understand this behavior too to an extent, but I think the cons largely outweigh the pros.
You can always set the filename as one of the displayed fields if you really wanted something displayed since the filename will always be populated (and since that's where Artist and Title are pulled from anyway). OTOH not having a clear indication that something as essential as the Title and Artist missing is a much bigger issue.