For the browser neither disk space nor memory usage are in top 10 of list of priorities.
On the first place in the list, by the way, is safe browsing experience. Rendering is only the second. And that one is the reason why browsers create separate processes for each window/tab. And that one is quite against low memory usage and longer battery life.
Browser are designed for the case when user interacts with them "full screen" - as the main application on desktop and so design decision are focused on that.
Browser can afford multithreading/multi-processes but far not all applications can afford loading all CPU and GPU cores for rendering "Hello world".
That's why people who use VSCode prefer more lightweight solutions for "config file editing" scenarios.
It’s not a browser. It’s a webbview-driven GUI library. The platform webview is in charge of rendering the UI thread; or more, if the programmer desires. No idea where “safe browsing experience” factors in here.
Definitely not as good as full native, but a definite step up compared to Electron.