The article itself is basically a wrapper around a Hacker News post where this was previously discussed.
<a href="http://news.ycombinator.com/item?id=2317804" rel="nofollow">http://news.ycombinator.com/item?id=2317804</a>
When a public component uses one JavaScript engine over another it is probably not a bug or an oversight. My guess is it is an internal dependency and scheduling issue at Apple. The team behind UIWebView is probably downstream from the Safari/Nitro team and they didn't get the new bits in time to ship with 4.3. Full screen mode may well depend on UIWebView and not the Safari app components.
Since it's not present in UIWebViews either, sounds like a bug that it's only available to Safari, rather than a grand conspiracy theory. UIWebViews are pretty important to a lot of native app development.
If this is anything more than a bug, it's really troubling. There is really no possible justification for not allowing full screen web apps to have access to the Nitro engine.
Or maybe yet another case of Apple doing it because "they can"?<p>I noticed that people have tweeted this to Gruber but he hasn't mentioned it in his blog yet.