You go on a list for acting smart, and they dump it with a cellebrite same as at the border.
They would have to individually steal keys from every OEM, in GraphenOS' case meaning Google. Then they'd have to do the right dance to fake the right stuff to satisfy the Secure Element(TM) and get it to let them use the data encryption keys. Which, by the way, I believe requires forking over a hash that may vary among individual phones; you have to know which version of the appropriate stage you want to fake.
... and you'll excuse me if I'm skeptical of your confident statements about what TLAs do or don't have access to, especially when you start talking about keys that don't exist.