The logic surrounding StarClan is steeped in a lot of misconceptions and retcons.
This is due to a couple things. One, is that the authors never seem to agree on how it works, and authors will contradict their previous statements constantly. The other, is that people make TONS of headcanons of how StarClan works. Many will present StarClan as an untrustworthy or evil force. Some will just paint them as incompetent, or full of the same biases and poor judgement as the living. Some will have them be scary, the wounds that killed them bleeding for eternity, and some will say that the logic of StarClan dictates that even though they can see the future and want to help the living, no matter how hard they try their prophecies all come out as a garbled mess.