Why doesn't @contenteditable work on the iPhone?

contenteditable has been added to iOS 5 beta 2, according to one of the developer videos from WWDC 2011. I suggest signing up to Apple's Safari developer program and downloading that video from the WWDC videos page.

If you sign up to be a Safari dev, you also gain the privilege to submit your Website to their online iOS Web app gallery.

Edit: I've confirmed this works on my iPad running iOS 5.0.1. Try it out here: http://www.quirksmode.org/dom/execCommand/

It works, kind of. I thought contenteditable doesn't work on iPhone before. When I set a div to contenteditable I couldn't move the cursor/pointer to where I wanted to move it. But, when I was fiddling around XHTML with contentEditable within iBooks.app on iPad, I found that "execCommand('insertText', null, 'foobar');" worked within Mobile Safari.