He probably lives in the USA where the FSB is less likely to oppress him than US government agencies are.
On the other hand, it's the NSA's job to read all the FSB's data. So by using the non-US-based program, you make it easier for the US government to spy on you.
Every time these discussions come up people sound like they think they're El Chapo or Ai Weiwei in which case yes don't use telegram. If you're an average citizen these agencies couldn't care less what youtube videos you share
FSB would try to read that information to try to damage the countries, to spy, to steal databases, to hurt people and so on.
If FSB could read private messages of US citizens it would be 1000 times worse than Google or Facebook reading them even accounting for leaks and misuse in G and FB.
G and FB is thousands engineers who love unicorns and rainbows and are extremely offended when the see a person wearing MAGA hat. FSB is men who regularly drink vodka, who are trained kill, who are not allowed to leave Russia, who are constantly told that Russia is surrounded by enemies.
Don’t compare G and FB to FSB.
(I doubt FSB can read Telegram.)
And have a pet bear that plays balalayka.