You’re confusing a core principle of bitcoin for the way the core principle was written down. It’s (obviously) a core principle of Bitcoin that coins never be frozen or stolen by any action aside from a mistake by their owners. However, that’s not the question we face if a CRQC becomes reality. The coins *will* be stolen or frozen, there is no other option [1]. In the face of that, you either pick that they be stolen by some QC startup, or you pick that they be frozen by fork. Also…

[1] There is actually one other option. If the keys for the coins were created with a seedphrase-based wallet, we can allow them to be recovered by their owners, but *only* if we freeze vulnerable spend modes!