I mean, that's one imaginary scenario. On the other hand, it's quite likely that upon a match the offending picture in full res is stored in an enclave on your device, and/or encrypted in the cloud, in such a way that it cannot be deleted by the user.
If they know this attack is possible, Apple, not being idiots, will cover their asses in court by saying that a match is merely strong evidence that the user may have had CSAM on their account, but that it cannot be said for certain unless the full image is obtained by the authorities, and that the full image should be where they say it is, with the voucher made by the device.
Because of that, prosecutors are unlikely to want to move forward without better evidence: Apple may very well testify for the defence if they do, and judges will ultimately chew them out. So yeah, I suppose rashness and incompetence in some parties may lead to a very uncomfortable situation, but ultimately it is likely that the police would be reprimanded for it and that it would be a lot more cautious afterwards.