The html_template is generally only used if you also set the view_id to "html". Otherwise, Prodigy can't really know where to use the template and how to incorporate it into the existing interface.
That said, the choice interface does support HTML content as the main input (e.g. the question / content to collect choice feedback on). If a "html" key is present in the data, the input is rendered as HTML. So I wonder if you can trick the interface into using your template by adding something like "html": "" to your task?
The same works for the options, so you could also try {"id": 0, "html": "", "some_other": "stuff"} in the individual options. I haven't tested it yet, so there might be unintended side effects.