The API Documentation and Help states:
If the help URL is requested in a common web browser, a HTML styled version of the JSON help will be returned. Otherwise, the JSON help will be returned.
However, I would expect that adding ?type=jsontext would override that behavior.
Also, making that request from my app also results in HTML instead of JSON.
/helpor the/help/method?method=...url?/helpdoesn't support a JSON version (at least not now, and its not a high priority).