It seems that they are not quite there yet. From the FAQ: "Voicefill sends the audio to Google’s Speech-to-Text engine, which returns transcribed text. [...] I

It seems that they are not quite there yet. From the FAQ: "Voicefill sends the audio to Google’s Speech-to-Text engine, which returns transcribed text. [...] In the future, we expect to enable Mozilla’s own technology for Speech-to-Text [...]"