I hear what you're saying. It baffles me too how one CRA can delete stuff and others don't. It makes you wonder how and if they verify anything? hey?
I don't know what to tell ya though - I'd still wait it out a bit. (?) But, you could send a letter similar to what you have and maybe mention that it was verified and deleted through another CRA and you're requesting them to validate where they are getting their information from or delete so you can resolve this matter since it is inaccurate.... (some sort of wording like that.)