I don't think anyone is arguing there are mobile OSes that have zero fragmentation, unless there has only been one release. It's about the degree of fragmentation.
Makers of iOS apps can safely develop for iOS 4.2, since more than 97% of iOS devices have at least that version installed [1]. IOS 4.2 is little over a year old. Can a full time Android app maker afford to solely develop for Android 2.3 (which is also a year old)?
If you were developing an app today, you'd probably want to target 2.2 as a baseline profile. That covers 90+% of the devices out there, and it excludes some of the first and second generation devices that are going to be the real pain to develop for. In six months to a year, 2.1 will be off the radar for developers:
Makers of iOS apps can safely develop for iOS 4.2, since more than 97% of iOS devices have at least that version installed [1]. IOS 4.2 is little over a year old. Can a full time Android app maker afford to solely develop for Android 2.3 (which is also a year old)?
[1] http://www.marco.org/2011/11/30/more-ios-device-and-os-versi...