I have a question about Telegram. Let's say I have a number in my contacts, but the other side doesn't have my number in their contacts. So I can now see their

I have a question about Telegram. Let's say I have a number in my contacts, but the other side doesn't have my number in their contacts. So I can now see their name and picture and "last seen"? But can they see the same thing about me without having my number saved? Do they get notified at all? Seems really odd to do this one-way.