We do, but that would require the company to lie about what they are doing with the app. At Twitter's scale it's very possible that someone would notice and leak that.

The goal as I imagine it is to go from "Hundreds of Twitter employees can definitely access my messages today and anything I've sent and received up until now" to "Twitter will likely need to perform a MITM attack to read my messages starting from the moment when the attack was performed. Maybe they have a secret backdoor, but it's probably too valuable to use on my cat photos".