[he opens his mouth to say that maybe the baby wasn't dead, but, the baby was very dead and he knows it, so he closes his mouth again]

...Seraphim are born from the earthpulses, usually. I don't think that was a lie we were told. But we've never seen that happen ourselves to verify the exact process, and no one's ever said it's the only way for seraphim to be born.

It could also be an anomaly that no one was aware of as possible. Maotelous was being hidden near that village, so it must have been on top of a strong earthpulse. The events that took place there could have caused something to happen that no one expected.