Missing an important part here: Telegram and co. is a cloud storage service where as WhatsApp, Signal, Threema are not. Think about this... your messages are stored and not delivered and deleted on the server. Telegram has the encryption and decryption keys but claims there are in different countries/jurisdication. So is this safer than deliver+delete? I think NO.

I wished somebody would analyze if WhatsApp protocol is using encryption also on iOS, groups and images as this website claims: https://github.com/WHAnonymous/Chat-API/wiki/WhatsApp-incomi...