Its UI runtime is Qt and its JS runtime is Node.js. No Chromium here :) it makes super-small, low-memory apps.
It's using the same JavaScript engine as Chromium, which is of course developed by Chromium and is part of it, but without the rest of Chromium, as Node.js always has.
It's a great example of synecdoche [1]. :)
Anyway, it was just a misunderstanding based on poor writing on the web page.