that will give him less privacy not more imo.
Not if you have your phone number hidden as well, which is something everyone has (or at least everyone should have it hidden).
And without username and with phone number hidden, the chances of situation like in the first post is basically non existent.
I don't know, but there are some cases where your number will be hidden without a username set on your profile. Some people can still see your mobile number. I don't know if it's just a feature for a specific person, maybe the premium users or something.
Is anyone using Telegram Premium who can confirm if that feature is available for them? Because I have been contacted before at my mobile number, which I'm very sure is hidden and has only been used on Telegram, which makes me use online-generated numbers for Telegram, which is not linked to any of my identity.