Everyone in Russia is familiar with Navalny, though. I mean, it's not like everyone in USA personally met Joe Rogan or Elon Musk (not sure if these are the best

Everyone in Russia is familiar with Navalny, though. I mean, it's not like everyone in USA personally met Joe Rogan or Elon Musk (not sure if these are the best example, since I am not from the USA, but I'm guessing they must be good enough), but you probably are kind of familiar with them and vividly remember their voices. You don't have to be a CIA agent spying on them to recognize them over the phone. That being said, as I already told, I think it is plausible. People often don't recognize other people by voice, despite being very much familiar with each other.