Well, let's back up. Lie detection is not completely unsolved. Polygraphs are used extensively by security services for clearance screening. They are reasonably good barometers of truth telling. They are not good enough to be admissible in court, but that doesn't mean they have no correlation to the truth.

Even if all this "AI" does is match the quality of a polygraph, it is probably extremely useful in screening people rapidly at the border.