It seems a bit different than that, at least according to the original story when incest still was around. The mother was Mythic, the father human and Ester knew the mother for a while so she would know her mythic type.
However when MC does the tests at the library some new and interesting things happens. So more likely it is the half-mythic portion making it different, similar to the original Dragon Ball Z story where Gohan being half-half was supposed to be way more powerful than Goku could ever become. Before they rewrote everything into what exists now.