Dangerously for privacy, a friend's account keeps getting notifications of when my contacts join because the app must have automatically scraped my contacts from my account to theirs when I was setting up their Telegram a few years ago (it was a used phone so all I can think of is I might've used my SIM card to test things out during the process).
Since we can't access this "central" list there's no way to clear them up apart from as they join, one by one.