Apple changed (or fixed) UIWebView.loading property in iOS 6 (Beta).
Details:
When you load a page with multiple frames, (void)webViewDidFinishLoad:(UIWebView *)webView is notified multiple times. On that notification, if you check uiwebView.loading property
In iOS 6 (beta 4):
You will get loading == YES, until all the frames are loaded.
// And that's more intuitive
In iOS 5:
You will get loading == NO on the very first frame completion.
// So it was rather hard to know when all the frames are done loading.
So now showing a spinner until webview is fully loading should be more reliably shown.