“Did Apple actually claim Cellebrite couldn’t hack into it,”
Read swordmakers comments here on FR. He posted all kinds of garbage making claims that not even Apple could hack the system.
I have read Swordmaker's posts in many threads, and I don't recall ever seeing him write something that said that Apple could not even hack into its own system, although hacking into a system to obtain unencrypted data would likely be quite a different thing than hacking into a system to do a number of other things. I did the courtesy of reading this thread completely, and read one of his comments that said "...Apple is making it impossible for them to even KNOW anything about their customers by putting their customers' in charge of their own data and privacy, not Apple. Apple does not have the keys to those data and cannot decipher it. Apple cannot sell what it cannot read..."
This paper explains the details of what Swordmaker stated above is true: iOS Security for iOS9 or Greater
I am sure that it is viewed as Apple propaganda by some (possibly even you) but if so, I would be interested in how you think they can get around this themselves.