BITB will work much better once we can compile and run popular browsers via WASM. Just look up the user agent, find the matching browser and render it to a draggable canvas. Obviously you'll find something off if you're not using Windows/MacOS. But that still leaves 99% of desktop users vulnerable.
Browsers via WASM doesn't gain you anything unless you're also shipping the matching OS via WASM which, even if that happens to be Windows 2000, isn't going to be fast enough to be believable. Without shipping the OS all you've got is a really weird looking browser window that still takes forever to load and run.
With some clever animations it can even phish a majority of the mobile too, like some Safari new tab sliding into view. They probably can't exactly replicate it as they can't actually move the address bar and title views etc. but they'd pull something good enough to get most of the non tech-savvy mobile users.
