I’ve had an iPad that’s been locked for at least a year (forgot pin) and I don’t have a computer that runs iTunes to plug it in to and unlock it. Would this get past that?
If you have the proof of purchase, an Apple Store should be able to unlock it for you.
And you still hold the private key, from what parent said having the store unlock the phone means that it will be factory reset so they still can’t access the data on the phone.
The key needed to decrypt the phone contents is generated and stored in the Secure Enclave, a separate piece of hardware+firmware on the phone. When the user providers their password/pin, the Secure Enclave checks to make sure it's correct and then it will decrypt the phone contents and make them available but the actual decryption key never leaves the secure enclave and isn't accessible by the main OS.
Users can choose to enable Activation Lock, which means that only the owner or Apple can allow someone else to erase the device and set it up from scratch. Users can disable Activation Lock at any time. The only time that users can't disable it is if they forget their iCloud credentials. That's when they have to go to an Apple store and prove that they own the device.
Users only need to get Apple involved if they forget their iCloud credentials.