The reason the FBI could get a third party to access the iPhone is because DRM, unlike real encryption such as what is used in Monero, is based on snake oil rather than sound mathematics.
Edit 2: The same or similar Apple DRM that the FBI broke, was used from 2009 to 2014 to censor Bitcoin and is currently used to censor Monero
Are you saying that Apple is lying when it says the user has the private keys and not Apple?