I think your parent’s question is completely justified by having anecdotes. They aren’t stating a fact, they are raising doubts of a claim. One does not need scientific evidence to raise doubts about a claim which it self has limited—and sometimes no—evidence behind it. Repeated real world examples are sufficient for such doubts.

Now if FSD proponents want to stop people from having doubts, they need to run several experiments in very diverse settings (as diverse as real world driving). In the absence of sufficient evidence, a skeptic is completely justified.