What the metadata proves
The schema.org inLanguage field proves listed language support at product level. It does not state whether each code applies to interface, subtitles, audio or a combination.
GTA 6 supported languages, subtitles and voice audio
Xbox’s official structured product data lists 13 language codes. Polish is included and Hungarian is absent, but the field does not separate interface, subtitle and voice support.
Confirmed checked: source: Xbox Store Hungary — Grand Theft Auto VI Rockstar Games — Grand Theft Auto VI
The 13 listed language codes
German, English (US), Spanish (Spain), Spanish (Mexico), French, Italian, Japanese, Korean, Polish, Portuguese (Portugal), Russian, Simplified Chinese and Traditional Chinese.
Polish and Hungarian
pl-PL is present. hu-HU is not. A Hungarian-language storefront does not mean the game itself supports Hungarian.
Update trigger
A Rockstar support article or more granular PlayStation/Xbox product field separating interface, text and audio.
Decision: Publish only the 13-code fact today. Keep subtitle and voice claims unassigned until an official source provides the split.