I was fully expecting something along the lines of "Oh, and SwiftUI will compile to WebAssembly allowing your apps to look just as awesome and run just as fast in Safari."
Safari isn't the point -- running on other platforms is. Market share for iOS globally is nowhere close to Android; in India iOS is only about 10% so if your SwiftUI app could run in Chrome on Android and is installable as a PWA, you open up the rest of the handset market.
True. in fact they have a vested interest in not making this happen, but someone will. This looks really impressive and i've grown to like swift quite a bit.
Probably still in alpha...