In fact thanks to a recently leaked presentation slides posted by Benjamin Geskin (via AppleInsider), it shows an alleged Foxconn presentation in which it revealed that Apple did indeed toy with the idea of a rear-mounted Touch ID, but decided to give up on the idea later on. The slides refer to an iPhone with the codename “Cyclops” and the Touch ID sensor which is being referred to as “Mesa”.
The slides also seem to hint that are some delays with the iPhone, which meant that Foxconn could not start production of the devices as planned. This seems to be consistent with the rumors that the iPhone 8 could face supply constraints at the start due to production issues, meaning that unless you move quickly, there’s a chance you might not get your iPhone for several weeks or months.
Take it with a grain of salt for now, simply because presentation slides can be easily faked, but we suppose if there is some consolation, at least this seems to be more “evidence” that the rear-mounted Touch ID which everyone seems to hate will not be making the final cut.