Ok fair enough. I've never heard them boast about this as an advantage in their other material (release notes, YouTube videos). I don't think this is really an advantage until they do actually have a different engine that you can swap out. Right now it feels very tied to Chromium.
They have however done some cool things with running Swift on Windows and rendering the UI via Windows APIs.
> This means we may offer a WebKit version one day, or even build a rendering engine of our own. Time will tell!" [0]
[0] https://arc.net/faq