Why is that so suspect? That's just TNO-style encryption- as in, you encrypt it going up, and download the encrypted chat history, before decrypting it using your login information.
Now, if they're sending it back to you as plaintext? Sure okay, that's reason to be concerned. But simply getting back your chat history isn't any reason to doubt the end-to-end encryption.
Now, if they're sending it back to you as plaintext? Sure okay, that's reason to be concerned. But simply getting back your chat history isn't any reason to doubt the end-to-end encryption.