Then its not end-to-end encryption in any way that matters to me.It doesnt really matter actually, Twitter would control the endpoint. It's how other E2E services comply with law enforcement for ex, the endpoint app can forward data to be read without having to MitM the encrypted stream. tldr Twitter doesnt need to hold the keys, they can get the data after it gets decrypted on the client.
So I was right it is only end-to-end encryption except for twitter, friends of twitter, the government, and anyone that can convince some twitter engineer to hand over the data.
It might as well be unencrypted.