Thank you for providing some more detail This is the expected behaviour of the JSON API — it will return the question and choice names (including their group hierarchy) and not their label as you can do with the CSV or XLS exports. Please refer to my explanation here as to why there are “missing” items in the JSON response compared to CSV or XLS.
You will have to do some post-processing on the JSON data to get the labels back but, as has been recently requested here, we may look at a more convenient way to do this in the future.
This is the expected behaviour of the JSON API — it will return the question and choice 