I've not learned Rust yet, but unless it does behave really weird, I can't believe that Electron and Qt have roughly same RAM usage. In my experience Electron has usually 2 to 3 times higher RAM requirements than Qt application of similar scope.
In the context of the article, the UI is in HTML/JS and the business logic in Rust, thus the RAM is not so high.
On the other hand, Qt QML embed it's own JS engine which is not resources light.
For a GUI app, business logic is usually not where your RAM budget goes.
Qt with QML Hello World ~40MB of RAM
Gtk-rs hello world ~20MB of RAM
That's wrong.
QML has two mode: one "interpreted" ( the javascript-esque) and one that can be compiled to native C++ without js.
And WebKit / webview itself is a plugin for Qt, it is absolutely not required.
... that is entirely false. Qt has its own scene graph renderer which has nothing to do with WebKit.