I think what is concerning is that they are expanding into Google Cloud and NVIDIA to run with it too with their versions of confidential compute, which if I remember correctly are not as well verified as Apple PCC and a little harder for researchers to get their hands on.
Apple uses a key ceremony process where no single party has access to all the keys required to sign hardware, meaning in theory they can’t just sign malicious hardware. However, I’m not sure how Google and NVIDIA play into this and I don’t think they’ve provided much detail on it. I think it seems a little rushed to get the features out since they fucked up with initial Apple Intelligence release.