We know that. The fact that the information is available somewhere makes it a FR and not a bug. We just consider "post was edited/improved by its author" fundamentally different from "post was fixed by someone else"... and the current interface shows exactly the same visual cue for these two states.
You know, Stack Overflow does list the last contributor (and edit time) in that "edited info" area, so maybe it's a useful idea to include more information than just "something was changed by someone at at least one time". ;)
But i think you're getting too defensive. Do you really think this feature would be useless? Because i'm just suggesting the idea be put there on the list of possible improvements, not demanding a "fix this by Monday, or else"...