These scenarios sound rather like "the wrong side of airlock" stories[1]. Why would China go through an elaborate scheme with fake child-porn hashes, when it can already arrest these people on made-up charges, and simply tell Apple to provide the private key for their phones, so that they can read and insert whatever real/fake evidences they want?
[1] I'm stealing the expression from this excellent article: https://devblogs.microsoft.com/oldnewthing/20060508-22/?p=31...