So is Signal and at least that is secure.
I'm normally on the Signal side of this argument, Telegram is trash and should not be used, but basic features like message editing are legitimate requests. I use Signal heavily and a number of times a day at least I or someone I'm chatting with corrects a previous poorly phrased or incorrectly typed messages. Because Signal has no mechanism for that, it usually involves retyping most of the message or the relevant word and adding an asterisk. I believe if Signal had built-in message editing support it would be used far more than I currently see corrections.
To be clear, I would expect Signal to allow me to see previous versions of a message and clearly indicate that it's been changed, but message editing is a valid feature that Signal should absolutely implement.
Further, the goal of Signal is not to work well for people who are accustomed to the various quirks of text-based communications that have existed since forever, but to provide a secure, modern communication client that normies don't find difficult to use. Message editing has become a standard feature of any usable modern messaging client.