> Few 'bugs' in implementation and you have a nice backdoor.
This holds regardless of whether WhatsApp is a blackbox or not. Now, that doesn't make the claim of end-to-end encryption verifiable, but if you take Facebook's word for it, the bug bounty should be about as good a stalwart as there is against implementation bugs.
It's kind of complicated. There were Brazilian bans in 2015 and 2016. Whatsapp has had encryption since 2012 but it was a bit half arsed. It now seems good. I guess the courts could still order the metadata of who's been calling who though. It's a bit unclear what exactly the courts did order.