So it is details about the sacrifice and not the birth of the dragons.
Birth of the Dragons was quite clear. Blood magic and the increase in magic during the time led to their rebirth.
We fleshed out the other side reasonably well, imo, above
Detailing the Blood Magic, as Kep says would have made it seem more like science. And there is no reason for Dany to learn how it really worked, except but Mirri telling her.
Detailing it wouldn't have made any sense imo.