With the present state of politics—lack of both government and corporate ethics, deception, availability of much fake news, etc.—there's no guarantee that you could be certain of the accuracy of any information about this no matter what its source or apparent authenticity.

I'd thus suggest it'd be foolhardy to assume that total privacy is assured on any of these services.

BTW, I don't have need of these E2E services and don't use them, nor would I ever use them intentionally to send encrypted information. That said, occasionally, I'll send a PDF or such to say a relative containing some personal info and to minimize it being skimmed off by all-and-sundry—data brokers, etc. I'll encrypt it, but I always do so on the assumption that government can read it (that's if it's bothered to do so).

Only fools ought to think otherwise. Clearly, those in the know who actually require unbreakable encryption use other systems that are able to be better audited. If I were ever in their position, then I'd still be suspicious and only out of sheer necessity/desperation would I send an absolute minimum of information.