OK. A friend was anxious to try it, so I installed it. About 50MB download for my Android device. Friend's android version was too old for the general app, but his linux laptop supported the text (CLI) version. His install for the laptop was only 25MB.
To my surprise the operation/presentation is not like in the website animations at all. It's just like Telegram or Briar or Session on my phone.
But unlike Session or Briar, there is a Re-Edit option for messages. It even allows posting/sharing image files. It also has a live voice-call feature (but I was unable to try it cuz my friend's laptop was not set up with sound.) In any case, it would seem like a fine way to make a private/encrypted voice call.