You’re wrong in your belief. We all know what a WebView is, but what is being discussed is bundling WebKit vs. bundling Chromium (like Electron does). A solution that bundles only a WebKit engine would be smaller than one that bundles a Chromium. What is your objection, specifically?
Building on top of a framework that bundles a Chromium should result in a smaller application than building on top of a framework that bundles a WebKit. As an example, compare Vivaldi (Chromium) and Orion (WebKit).
Chromium has many more batteries included though, such as V8/Node.