As is the case with Apple's software certifier key. AFAIK this is what we currently have to assume since Apple doesn't specify how the update process for the secure enclave works. If this is the case it doesn't change anything, the certifier key is already like a master key.
Replacing the firmware (Secure Enclave or not) with a version that doesn't include rate-limits and auto-wipe isn't the same as having a crypto backdoor. Right now, your data is still protected by the complexity of your passphrase. This is not true for your scenario.
