Really? I was like "wao, he has found a way to break encryption" only to figure out he is decryption using the key. End to end encryption is all about preventing man in the middle attack. Not about preventing a second way for decrypting at end points.

I don't think he alluded to breaking / cracking the encryption. Decrypting messages is not that same thing as breaking encryption. In fact he demonstrates how Whatsapp have done things properly and at the same time demystifies how the whole thing works. He doesn't actually explain end-to-end encryption, but only indicates that that is the mechanism used to transfer the secret key from the sender to the receiver.

And further, it calls into question the ~FBI report's claim that the file was "end-to-end encrypted", so they couldn't inspect it.

And as others note, if the key had been deleted, they should have said that it had.