The question is whether this actually is E2EE, as it’s easy to fake by using a man in the middle attack and hard to prove. The only real way to prove it for sure is to run a third party security audit, like Signal does.

Taking down the old system doesn’t inspire confidence either, as this downtime could easily been used to interrupt old conversations in order to implement a way to decrypt the messages on the servers before passing it on to the actual recipient, as all keys would have to be re-issued.