For instance, please explain why it took until iOS 6 for HTML/JS apps to access the user's photo and video libraries through [HTML file upload]
Because exposing a user's files to any in-page behavior is a security risk and needs to be handled in clean managed ways with limited APIs?
If Apple were sincere about making the web its API in iOS 1, it would have put a "clean managed" media chooser in place since iOS 1.
Imagine how bad it would be if "it works on the latest release, but only on these specific models".
Firefox already does this with its WebGL driver blacklist. It does not support WebGL on pre-OpenGL 2.0 GPUs, such as the integrated GMA 3100 in the Atom N450 processor in my laptop.