Cause for them to use it overseas it needs to be unblocked internally (to Russia)? Russia can always "whitelist" some applications for government officials too. Or y'know not rely on third-parties and roll their own solution, not like Signal's protocol isn't open sourced.
I don't understand the point you're trying to make.
Blocking Telegram helps Russian intelligence operations by making it appear like as if the Russian government did not have access to the vast majority of conversations over Telegram.