Probably everything uploaded after the intercept is in place if you can convince a court to compel it.
One option is to release a malicious software update, sign it, publish the signature on the public chain, and then simply not release the binaries until after whatever associated gag orders there are (if any) expire. Apple gave themselves a 90 day timeline for this before they'd even be in violation of their promises.
Another option is to use the cryptographic keys used to make the hardware that attests to the software running on it, to simply falsely attest to what software is running. Unless Apple's somehow moved those keys outside of the courts jurisdiction (which means outside of Apple's control in the case of most courts) that should be within the courts power. If they can still create new hardware, it seems likely whoever is making that hardware must still have access to the keys...
Both of these attacks are outside the "threat model" proposed, because they are broad compromises against the entire PCC infrastructure. The fact that they are possible and within the legal systems power... well... why are we advertising this as secure again?
The main value of this whole architecture in my mind isn't actually security though, it's that it's Apple implicitly making the promise that they won't under any circumstance use the data, or let anyone else use the data, for business purposes (not even for running the service itself).