I am surprised at the skepticism that TouchID would not work for some people. This has been a known problem since early on. While TouchID works flawlessly for many people, if not most, there are also many people that never worked well TouchID, and that not due to user error. In fact, for many people, TouchID would work 100% of the time for days, and then the device would suddenly "forget" the prints entirely, and fail to recognize the user. I have seen multiple cases where people report the same problem with FaceID -- for them. I believe them, and it is not due to user error. But FaceID works 100% of the time for me.
Just believe the OP and stop trying to "fix" him or his problem, and sympathize with his demand for FaceID, since this has been a known issue for many people for a long, long time, and it also happens with some people with FaceID. He can register the same finger for 5000 times if the device would let him, keep his prints in perfect condition, and the problem will still occur for him. And it could recognize him for days, and then suddenly not. Again, for some people, the same thing happens for their faces.