None of the typical criticism against Telegram is directed at whether this is the case or not; usually people start by assuming Telegram is something it doesn't claim to be (a super-secure encrypted-exclusive communications app), and then proceed to attack the scarecrow by pointing out that it's not encrypted-exclusive. Whereas Telegram just says it provides the ability to encrypt your chats if you want to, but otherwise it's more of a multiplatform social platform. It specifically does not state that its sole purpose and raison d'etre is that you, either as a private person or as a terrorist or whatnot, should feel safe and secure using this tool at all times and expect to be untraceable.

The point I'm making here is, if a box needed to be checked and they checked it (properly), then people ranting "ermagerd what about all the other checkboxes that you don't need but other system with different priorities and mission statements have" isn't really useful criticism against the project. Let alone suggesting Signal etc as an alternative, which is like suggesting a raspberry pi to someone wanting a macbook experience.