Netflix only shows audio/subtitle tracks that are in languages they think are relevant to you.

But nowadays you can configure additional visible languages yourself on the language settings page (checkboxes under "Programmes & Films Languages") without changing the UI language: https://www.netflix.com/LanguagePreferences

Seems silly to me not to list all available languages. I would have never known this if you didn’t tell me. I didn’t slipped my mind to consider its a Profile Settings thing.

Apparently it was done for UX reasons: https://www.quora.com/Why-arent-all-subtitles-available-in-a...

But that seems weird to me - just show the more relevant languages first, then, so they don't need too many button presses.