Leather Case posted by Kumamoto Technology from China in some way is probably confirming that the iPhone 8 or iPhone7S/7S Plus may arrive with the Touch ID fingerprint scanner on the back, as you can oberve on the recent leaked picture. There was before another aluminum back cover with the Touch ID scanner on the back from the same source weibo, as well. This recent post from China was made in August 18,2017.
Before related post: iPhone 8 UPDATE. Fingerprint scanner on the back.