It looks as though Apple had already been “backdoored”. Probably more than once.
Why do you say that? This article says exactly the opposite.
The vast majority of iPhones, the iPhone 5S, 6, 6 Plus, 6S, and 6S plus which now comprise approximately 450 million iPhones combined are NOT susceptible to the hack that the FBI claimed opened the iPhone 5 and 5C. . . which maybe represent approximately 100 million devices. The other iPhones such as the iPhone 4S and lower, an estimated 200 million still in circulation, were always openable.