Easy: the problem with memory is not the WebView nor is it displaying HTML using that WebView. The problem is the layers of layers of JavaScript (frameworks) running in that WebView when using Electron or the like.
I am working on something similar, HTMXNative as part of a bigger idea called interscri.pt that can use either WebView or native for rendering and the difference in memory consumption is somewhere between minimal (or even undetectable) and modest.
From a baseline that's also modest by current (native) standards.
I am cursed that I always have to work on legacy products that were built many years ago and didnt consider these things.
I hope we eventually get a good/simple language/framework that can compile to native code. Even react native for mac/windows is good enough now.