Planting false evidence is getting a new twist here. The attacker doesn't even have to make a report! The victim's computer does it for him. Disk encryption malware may have new successor. Effective and scalable extortion as a service.
iOS 15: "WTF is this?" SWAT team crashes through window
The example is somewhat contrived.
If a 'friend' takes your phone and has access to it and then uses it to take images of CSAM similar enough to the original image that it triggers the hash match and does this enough times to go over Apple's threshold to flag the account after these images are uploaded to icloud without the original phone owner noticing then yes it might cause a match.
At that point the match is probably a good thing (and not really a false positive anyway) - since it may lead back to the friend (that has the illegal material).
Or anyone who can just text you since imessage backs up to icloud automatically...