How to change snippet.defaultLanguage of YouTube Video using API

I am using YouTube Data API Reference to change Video.snippet.defaultLanguage (https://developers.google.com/youtube/v3/docs/videos#snippet.defaultLanguage) using the following API call

        var resource = {          snippet: {            title: video.snippet.title,            description : video.snippet.description,            defaultLanguage: 'en-IN',            categoryId: video.snippet.categoryId          },          id: video.id,          localizations,        };        YouTube.Videos.update(resource, 'id,snippet,localizations');

I got the above code from the Youtube API Samples example (https://github.com/youtube/api-samples/blob/07263305b59a7c3275bc7e925f9ce6cabf774022/apps-script/youtube.gs#L107)

Form trial and error, I understood that title and categoryId is important even though its irrelevant here.

I have also looked at similar code given by others in GitHub (https://github.com/search?q=language%3AJavaScript+YouTube.Videos.update&type=code), but unable to get a correct API call.

From the documentation, snippet.defaultLanguage is "the language of the text in the video resource's snippet.title and snippet.description properties.". So, it can't be set?