One additional note:
Your screenshot shows you’ve selected to display English forced subtitles. However, the file only lists the regular subtitles (no forced track).
Not correct. I have the same setting and my full English subtitles are selected either when the media only has a foreign audio track or if I select the foreign audio track when there is an English track available.
Also, forced subtitles are selected when the audio track and subtitle track (labeled forced) match. That would not apply in this case.
Also, I will note this is the official Plex Docker image (not linuxserver.io).
Edit: I hadn’t checked programs that have forced subs, so I just now added additional content to the test library. It doesn’t appear forced subs are being selected either.