I get it and I'm sure most people online have heard that phrase. I think what people may be used to is other users not being able to see 'deleted' posts. But everyone is pretty familiar with everything is forever online type thing. Maybe not with the notion of everything being forever and for other users too. I think perhaps the unspoken part I'd about everything being forever and accessible (for corporations and intelligence services) lol.
But yeah, I'm not arguing against anything you said obvs