Yep - I totally agree with that.
That’s why I think it would be better if the two ‘post numbers’ shown on the same screen agree (screen shot is in my post above), even if the post number in the URL (which usually needs scrolling) would still give away the actual post sequence number.
Given the scroller on the page knows the ‘visible’ number of each post, I’m not sure why this would be hard to re-use on the post dialog, but then I’ve not looked at the code either!