Agreed. Also, what is the actual iPhone app? Where was the ad(s) placed? Different kinds of apps will have different ctr. And ad placement is also very important.
Without context we can't validate your claims and hope to reproduce them. Thanks.
The 0.1% CTR apps relate to mobile games where there is little interaction with the ad is 'Word Seek Social Lite' The 4.5% CTR app relates to generalized RSS readers similar to FMyLife (ex: Softbaum's FMyLife for which we have a rev sharing agreement).
Hope this helps, of course since these are highly profitable, I can't share too much details.
An interesting linked article, though not really a comparison (unless I missed something, and they're the same games on different platforms?)
CTR will have as much (or a lot more) to do with the quality of the game and how ads are presented, than it will the platform or the platform's real-or-perceived demographic differences.
It's great to share, it's better to explain. Thank you.