Summary: In 3 cases, Mitochondrial DNA from the father has been passed on to the child.

Maybe this happens a lot more often than documented. In this case, it can throw the field of mtDNA testing and implications into question.

Conversely, maybe it happens extremely rarely and only in pathological cases (in the mathematics/statistics sense, if not the medical sense). In this case, it's just a medical curiosity and only important insofar as a doctor treating a patient with a rare disease may want to consider the remote possibility of this.