See? The whole "they knew they had to create me after they met me" thing makes no sense.
If Sisko wasn't created by them at first, he never would've met them because he wasn't alive. He can't very well meet them if Sarah wasn't possessed and hooked up with his dad.
So I think it has to be they just chose how to reveal information to him, at the appropriate times, so he could become a better tool for them to use.