I just tested that particular scenario on that particular movie even, in latest MC24, and it worked just as expected, as long as the alien-subtitle track is marked as forced. If its not flagged forced, then it is not selected, as it should be.
This is the only scenario when I personally would ever want subtitles, since I don't like watching movies/shows where I don't understand the audio, so I would definitely have noticed if it was broken.
Alien/Foreign forced subtitles are annoying me when they don't show up, so I take great care when ripping Blu-rays to ensure I get the right stream and mark it as forced, to ensure that it does in fact work properly during playback without manual intervention. And if that scenario would not work with MC, then I would've long fixed it. So this is definitely a scenario MC was designed for, because I ensured it is.
The subtitle selection logic is pretty straight forward, too. The option in the settings only controls when to select a "full" subtitle stream. If no stream is selected due to the settings there, it'll always try to select a forced stream instead, so as long as you have any forced stream, you should never end up with "Null" being selected. There was a bug in earlier MC24 versions that may have prevented that in some corner-cases, but in the recent version it should absolutely make sure of that.