Begin with the player’s available languages
Disney+ says audio, caption and subtitle options vary by title and region. Its help gives an additional branch when the wanted language is absent from the player: review the profile’s App Language. That makes the setting more than a cosmetic assumption in this particular documented troubleshooting path.
Read the version condition
Disney says that if a version exists in the selected app language, that version can be used and different audio or subtitle choices may appear. If that language version does not exist, it can fall back to English or another available version. The conditional wording matters; changing a menu preference cannot manufacture a regionally unavailable edition.
Keep a comparison record
Note the exact title, episode, profile App Language and the track choices before and after a deliberate change. Use the same legitimate account and viewing location. Keep the title and viewing location constant while comparing the selected App Language with the available player tracks, so the result describes one specific profile change.
Retain the intended profile setup
A language change can also alter the interface used by other people on that profile. Preserve the original preference and restore it if the comparison is unhelpful. If the desired edition remains unavailable, provide Disney support with the title and regional context instead of assuming a device factory reset or a second subscription will create it.
Questions, answered
Does App Language guarantee the requested edition exists?
No. Disney explicitly makes the result conditional on available versions.
Can title and region still limit the track list?
Yes. Disney qualifies language availability by both.