Man of Many Mothers is more of a short write up on a creature concept and a small organization around it. If all you wanted was a possible monster of the week, this still does not work well since the author mentions that a slow burn is somewhat needed to really draw out the actual horror themes in this write up.
The writing style features a somwhat comical approach to something that is supposed to evoke the primal fears associated with child birth. The piece itself leaves lots of negative space that will need to be designed around to present the creature, maintain the story thread, and give a rewarding build up and conclusion to the players. You get the feeling with the lack of mechanical information about the mothers and Neverborn that this was intended to be system agnostic, but then it mentions a 1st level fighter in one of the abilities.
I don't think the piece is terrible in totality, but it is treated more as a monster entry than an actual adventure. It is a 2 1/2 page write up of a single sentence design idea. "What if there was a monster that was reborn to a woman when it died, corrupting her in the process?" There is leaving things open for game master design space, and then there is writing something very roughly defined. I feel like this is more like the second option.