The JSON export with filter doesn’t work because the author forgot to add the lines:
        if option_box:
            self.option_box.parse_options()
            db = option_box.get_filtered_database(db)
near the top of the exportData routine (before line 36).
You might want to tell us what you expect the JSON export to do for you; this was an experimental diagnostic plugin, which I expect few people can really use.