I think your post should highlight the main idea: Telegram stores all messages in plain-text on the server. Even whatsapp doesn’t do that.
Seems to me like the “end to end” was an afterthought. Just to claim that they can encrypt messages. While 99% of messages are stored right there, and we must trust telegram not to give that data to anyone. Why should we?
I stand by my assessment at the time, but I haven’t checked Telegram since then and don’t know what, if anything, has changed.