Why are there so many pre established themes that “coincidentally” carry over from the original UFA/UFF – Rationalist universes? Will we ever get stories set before that tell how all this got set in motion to begin with?

All successful invaders/colonizers bring their cultural predilections/baggage with them, just as the English who settled Massachusetts and Virginia did, or the Spanish and Portuguese who settled Central and South America. The same was true of both the Rationalists and the black angels; it wasn’t coincidental. As for stories set in the past of both cultures… it’s unlikely, but I won’t foreclose that possibility.