What are "end-to-end security features"? They mention it once but then never again.
As far as I know, the term end to end is about communications: an exchange between two or more parties, or endpoints, which can be encrypted "end to end". I'm afraid they just dropped it as another term nobody knows the meaning of, so we'll have to find a new term to describe why Signal and Wire are better than (non-PGP) email.
"end to end" has been a term in common use in language since the 1800s meaning complete coverage. look it up on the oxford english dictionary for more details.
As far as I know, the term end to end is about communications: an exchange between two or more parties, or endpoints, which can be encrypted "end to end". I'm afraid they just dropped it as another term nobody knows the meaning of, so we'll have to find a new term to describe why Signal and Wire are better than (non-PGP) email.