The Thirteenth's time line flow (POSSIBLE SPOILERS)

[Iscah]

I mean, obviously they plan for things but it's a human level of planning - "we want to achieve X so we will need to do Y and Z". That doesn't mean they have some omniscient view of time and can see the "right" place to deploy Elidibus's rescued waifs from the Thirteenth - they just needed a pawn to fill a role in their current scheme, and Elidibus had some in stock.

Actually, the plan was for Cylva to die - the Shadowkeeper to be defeated by the Warriors of Light - and Ardbert broke it by not killing her as expected.