Yeah the scene where Kylo learns about the dyad was the oracle scene, which was cut from the final film, so the theatrical cut gives no explanation as to why or how he knows about that.
Maybe as he holds the Wayfinder in the opening scene, it could go on a dubbed extended expositional monologue.
In Vaders voice perhaps?
Also, having the wayfinder speak of 2 halfs of the dyad, while there being 2 wayfinders would be kinda poetic.