On the one hand, this seems nuts. On the other hand, the mechanism compared to all the other things biology can and has done doesn't seem that crazy.
Create egg, remove nucleus of egg, replace nucleus of egg with one or two nuclei from stored sperm that initiate replication and growth of the other species from there (depending on the exact mechanism which it sounds like they're still figuring out).
Compared with fungus that creates zombie ants (this is a real thing - https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis) and birds that change their eggs to match those of other species (https://en.wikipedia.org/wiki/Brood_parasitism) it almost seems tame.