Telegram has been sued over and over in many countries for refusing to provide that info, and kept fighting (both legally and technologically - via smart proxy-server rotation, addresses distributed over Apples/Google's push notifications etc.).
Here's the case for Russia - https://en.wikipedia.org/wiki/Blocking_Telegram_in_Russia (eventually the govt has blocked over 20 million (!) IP addresses, including Google's and Cloudflare's, and that disrupted 30% of the Internet in the country, but the app just kept working fine)
Schneier was very vocal after the Snowden documents on how the NSA has multiple methods to get hold of the data. If it's not via judicial means, it's via extra-judicial means. NSA considers Telegram's servers outside US fair game (i.e. hacking them is not a problem). GCHQ considers servers inside the US fair game. The two agencies exchange intel which allows them to bypass constitutional protections. This is old news.
As for Russia, China, Israel etc. The servers are outside their borders, and mostly they don't give a flying fuck even if it was domestically hosted.
Where's the documentation for this? Without documentation your assumption that there's any security is just blind faith.