Even a year before the release of iPhone X, there were many rumors that Apple would install a fingerprint scanner on the back or side of the device. There was also information that the sensor would be placed under the display. We already know that there is no Touch ID at all in iPhone X. Some publications suggested that initially Apple they tried to add it, but the technology could not be implemented. However, senior vice president of hardware development Apple Dan Riccio dispelled these assumptions.
In an interview with TechCrunch, he said that Apple “didn't waste time” manipulating Touch ID in any way, since all efforts were focused on Face ID from the beginning.
Note that the first rumors that the scanner in iPhone X will be placed under the display appeared back in May 2016. Over time, they only became more, and variations appeared. In particular, they assumed the integration of Touch ID into the power button or on the back panel. However, in July of the same year, analyst Min-Chi Kuo suggested that Touch ID would not be in the anniversary iPhone at all. In the end, it was he who was right.