So you need to make sure your code works on 3 different platform eventhough you're using a tool that's supposed to fix that problem in the first place?
I don't know the extend of WebView in Electron is it something common?
A ton of time and resources have been put into making web apps work across multiple rendering engines. These days, it can be difficult to have something break on one platform if you are using a modern development stack. The webview engines that Tauri uses are all quite modern, see https://github.com/tauri-apps/wry/discussions/202 for more details.
Worse, it needs to run on every version on every os. Windows 10 has an evergreen webview, but on Mac for compatibility reasons the webview is only updated with a new OS release.
Edit: This is not something you run into with electron. It's the reason electron apps are so big, they bundle the whole browser engine.