Any who pass across the River of Stars and into the Ruins of Ten Thousand Heavens cannot return to the Three Realms without a guide. It stands to reason that this includes their primordial spirits when they die. Perhaps even destiny cannot find souls once they pass through the River of Stars. If that is the case, then your Shifu may not have a way to know about those that live beyond the Three Realms.

[He answered, trying to use what logic he could to reassure her that it was not her Shifu's fault for not talking about such things. Even if he could not feel her emotions at the moment, she looked sad. Talking about her Shifu often came with tears even when she was happy. And he did not wish to give her reason to shed tears. Especially in his body.]