Good question- with Safari, we use the visible domain to help score the confidence for mobile websites. For native apps, we don't have any such "easy" confidence boost. So we have to fingerprint the app based on different features present in the image that is captured.
The system is computer vision / machine learning based, so even on novel sites, it will get better over time with more usage and training. We've trained it up for a bunch of the most popular sites already though.
Does this make sense?
