The HTML5 export should work just fine on iPhone. There are no engine differences when running on iPhones.
However IIRC there's a bug on iOS that makes iframes display incorrectly sometimes. The workaround is to add the scrolling and noresize attributes to the iframe tag as shown below:
<iframe src="game.html" scrolling="no" noresize="noresize" allowfullscreen="true" />
I threw in allowfullscreen as well so the game in the iframe can still use the Browser object's 'request fullscreen' (not yet supported on iOS but works in Chrome for Android).