Social anxiety is not at all uncommon. Therapy would only really be beneficial if the anxiety was causing problems in a person’s life. It could be that the person you replied to may need to lie down after a phone call, and is then fully functional afterward. Unless they’re bothered by this process or it somehow impedes upon their day-to-day life, it otherwise would seem like they already have their recovery mechanisms figured out and are doing well for themself. They’re playing the hand they were dealt, and they’re still in the game.