[NeoCortex]

a set can be 1 movie (regardless if it has one ore more edition), if you have this enabled:
settings > media > videos > include sets containing a single movie

That's not my case. I have that option disabled. But if there are two files, one 1080p and one 4K, the movie set gets created automatically, containing the two versions of the movie. Problem is, it's the same movie and now that we have Movie versions, that behavior should be stopped somehow.

I tag @jjd-uk to ask whether I should open an issue for this or if this can be looked into. It's not a problem of this feature, it's more, I think, a problem with how scrapers have handled this in the absence of Movie Versions. But now that they are available...

Edit: I suppose this might not be a problem for the future? Now when you scan a new version of a movie you get asked straight away if you want to add it as an extra version of an existing movie. Maybe that's enough to stop the creation of Movie Sets with two versions of the same movie, I don't know...

As I understand it, the "show sets of only one movie" option is only about displaying it as a set or not in the library. Even if it doesn't show as one, it could still be connected to a set.

For instance, if I have a single Star Wars movie in my collection, it will scrape as being part of the Star Wars set. It makes sense that it should do that. That way if I later add another movie in that set, I would then have a set of two movies.

Adding a second version of the same Star Wars movie, at this point, should just be added as another version of the one movie, which would then exist in a set of one again.

My general practice if I have a movie that is part of a set that I have zero intention of ever adding to is to just remove the movie from the set after it's scanned in.