I’ll probably end up doing this:

“He learned of a little girl he was supposed to take from Jakku, to the Emperor. The dagger exposed Rey."

This then explains why he’s going back to Exegol even if he already has a direct line of communication with Palpatine to transmit this news through (as evidenced by him getting the order to kill her father).

If it’s just the dagger giving Ochi visions of a girl on Jakku after killing her parents, then the Emperor would need to hold it himself to verify the nature of all of it as fact. But when Ochi never returns, he is left to assume that his granddaughter really does exist, especially after sensing her in TFA/TLJ.

As I stated on the Ascendant thread, this then blends harmoniously with a new Kylo line to Rey along the lines of: “The dagger showed you what happened to your parents, didn’t it?” So the dagger acts as a sort of family tracking agent upon coming in contact with somebody’s biological material. When Rey picks it up, she is shown the final moments of her parents. When Ochi stabs her father, he is shown his daughter.