Last time I checked (a few months ago) you couldn't use file:/// with a WKWebView at least on iOS8. Apparently, latest iOS9 beta allows you to load a local file.
Is there a reason they don't ship with a simple web server to server out the static files, similar to `python -m SimpleHTTPServer`?
Why would they want to? Both platforms have webviews that can render HTML from a file, or passed in strong form, or whatever you like. Why point it at an internal web server? If anything, it'd add overhead to the system that's unnecessary.
Apparently WKWebView does not support loading from file. That's why he suggested wrapping it in a localhost HTTP server.
The Android Cordova platform used to do this by including OkHttp but they moved away from that because it's now unnecessary.