Re: "... a misuse, which is contractually prohibited."
"End to end" should mean that, yes. However: consider that:
1) The app generates the keys; not the user.
2) WhatsApp changed hands for 19 billion dollars. Billion.
3) Facebook is the company that bought it.
Because the app (and therefore Facebook) knows the keys it would be trivial to simply store the keys somewhere and decrypt at will. If you think a bunch of weasels like Facebook spent 19 billion to not do that, then you have more faith in humanity than I do.
"End to end" coming from Facebook is, I very strongly suspect, marketing-speak designed to mislead people into thinking of the standard usage of the term (ie, client to client). If one of the ends happens to be Facebook then it's technically "end to end encryption"...they're just not specifying where the ends are and letting people assume it's client-to-client.
Biting the hand that feeds IT
