At least with the platform webview, you can:
1. Have some knowledge about what engine versions were available on what OS versions and make compatibility decisions accordingly.
2. Know that the browser engine is always there.
When it comes to trade-offs between "static linking" (Electron) and "dynamic linking" (Tauri), this is like cowboy linking. You have literally no idea what browser will open. I guess this isn't materially different from a remotely hosted backend but I still wonder of the merits.
And why communicate over a websocket, or not have a custom protocol that you can handle and register with the OS more easily? I like the general idea but this seems inferior to a webview in almost every way.
I do see how you might get things like extensions easier, but I'd rather petition the platforms to add extension support and close other gaps directly in their webview runtimes.
And is it just localhost under the hood? If so it reminds me of this Zoom security debacle a few years ago: