Earlier quoted context omitted.
You need to that anyway with ARKit, it only runs on A9 and A10.
Good catch, A9 isn't a few years back. My argument probably isn't as valid but I still think the guarantee of 2 iPhone generations is safer than the fragmentation of Android devices that would be "released in the past 2 years".
Not only is the install rate for the latest Android dramatically smaller than the latest iOS, but camera capabilities (and GPU horsepower to drive the AR itself) are all over the place, with no guarantee that the camera module in the phone will provide even a satisfactory experience, or that the GPU will be sufficiently capable.
Camera APIs on Android are also a complete jibbering mess, which adds to the difficulty of anything that seeks to work across all (or even most) devices.
One distinct iOS advantage isn't just that adoption of new versions is rapid, but also that hardware capability variance is low, so devs can be confident that their products work well, as opposed to barely working.