Just so I don’t get this comment killed, here’s some text calmly explaining that electron is based off blink, and implementing a browser in it is like using a text editor’s scripting feature to reimplement the cursor.
The difference from chromium is that the browser ui is implemented using the web tech, instead of native, which is not unusual either.
Firefox have been using slightly modified version of html and javascript to implement the browser ui forever.
Vivaldi and brave browsers use the same method as well.
Firefox has been switching from their custom markup (XUL) to HTML for its UI, and you’ll find that the web inspector in Chrome, Safari and Firefox are already implemented in HTML/CSS/JS (don’t know about Edge).