Hi again!
I think I haven’t expressed myself in a sufficiently clear and succinct manner. The observed behaviour is that only one of the two versions was initially “picked up” by my Plex server even though both files were sitting next to each other identically. 
If I ever back-up two versions at the same time, I’ll make sure to test this again to see whether that was a reproducible bug.
Additional:
And the expected behaviour was that my Plex server would sequentially process and list both versions as soon as the new “Mac and Me (19XX)” folder was detected. (Instead of me having to do some kind of Plex Dance as some people call it here. )
