In essence, all Apple devices have the exact same user agent string if on the latest firmware version, so we have zero way to differentiate device versions. All mobile reports are based solely off of user agent string, including screen size. Since we can't differentiate Apple device version and we don't actually collect screen size (we use a lookup table based on user agent), all devices listed under 'iPhone' all have a resolution of 320x480.
The article lists a partial workaround by using JS to obtain screen size, but that's about as accurate as we can get at this point in time since Apple does not include device version in the user agent or other HTTP header tags. We fortunately can get this data via iOS implementation (native apps), but not through a browser implementation.
Apologies for resurfacing your answer from a very old post, but I received the exact same question from an analyst in my company.
My question is, why is the reference screen resolution for iPhones the 320x480? This makes no sense, of the current iPhone models in circulation the vast majority is from gen 5 onward, so at least a 1136x640 resolution should be used as minimum size, if not the iPhone 6 one, as the most popular model. Is this something that can be changed somehow?
I know each iPhone version has difference screen size. But I have never seen "Apple iPhone 4" or " Apple iPhone 5" on devices report, and screen width or height of them on screen size report. You said that those user are very small number, but we checked own device for testing application many times. And I have checked device report filtering "Apple iPhone" again, there is not "iPhone 4" or "iPhone 5". (I attached those captured images.)
The Apple iPhone has three different resolutions/screen sizes, so it gets tracked by its screen sizes. Apple iPhone (before iPhone 4) has a screen size of 320×480. Apple iPhone 4 has a screen size of 640×960 and iPhone 5 has a screen size of 640×1136. So if you want to see Apple iPhone 4 or iPhone 5, run the Mobile > Screen Sizes Report and then look for screen sizes 640×960 and 640×1136. Now break down these screen sizes by Mobile > Devices and you should see iPhone 4 and iPhone 5 listed under their respective screen sizes. See attached screenshots.
I speculate that Apple iPhone 4 and 5 have less numbers hence they are not at the top of the list. So you can check for them through this method.