>> I kind of wonder why it took this long for someone to try this approach. It just makes a whole lot more sense on the surface.
I believe there are dozens of projects using Webview and market themselves as a lightweight "Electron". The development for these apps takes longer (as you need to test for different webview versions/vendors) and the end product is worse as some features are shimmed or you just choose to not support them due the effort required. Of course this depends by project.
I've developed a media player and considered webview. Soon enough I've found the limitations of safari, ie webview and even firefox webview on audio/video codecs is a blocker. Next was indexeddb and some random performance issues. It didn't took long to realise that it's hard to compete with native apps using Electron but its even harder using different webview versions.