It's pretty standard. I don't see it wrong. Everything has good and bad effect depending on how we are using it. I knife could be used to kill someone and the same knife we use in the kitchen. Telegram users can set a username if they want. In their privacy setting they can chose whether they want their number visible to others or not. Someone who is good man but concern about his privacy, for him it's a good choice. Exploiters will exploit everything.