Back when the iPhone first came out, and people were shrieking for native development, Steve Jobs announced his "sweet spot", which was the ability to write web apps for the thing (??). To support this position, Apple posted on their development site guidelines on best practices for modern web apps. These guidelines specifically advise against using browser sniffing (except under certain rare conditions which are not met here). One should instead use object detection.
Here are those guidelines. The document lists at length all the reasons not to engage in browser sniffing which are rehashed here. Basically there may be low or no correlation between the information in the user agent string and the browser's abilities. For example all browsers claim to be Mozilla, but it doesn't mean they all have the same feature set as Mozilla's Firefox.
Apple's developers who wrote this gallery appear not to have read this document, or more generally to understand the purpose of web standards at all. Apple's new HTML5 gallery touts standards, but it flouts all the goals of standards. The point of standards is that we can target a standard, rather than a browser. Apple violates the entire purpose, and deserves censure for this hypocrisy.