He works indeed in mysterious ways

Part of the reason the outsiders were an issue was they were worried about the ability to populate with them. The first stories about them was that a human mated with one and made a baby so grotesque os something like that. I don't quite remember.

So he is showing that even their origin story is bullshit and propaganda.

I think the reason to keep them seperated was also the birth reason. To make sure that taboo never happens.