So instead of taking the one in a thousand chance that its the wrong thing to do (which, from what I've seen, is generous) they should let edits languish for days or weeks until someone sufficiently knowledgable shows up? That just doesn't sound like a worthwhile tradeoff.
If something should not be edited through another account, then the software should just not allow it.
If it allows it, and delegates the check to moderators, then these moderators should either reject it if they are sure the change is wrong. In all other cases they should allow it.
You have no idea what the spectrum of edits is on SO. Why do you think your heuristic is obviously better, despite making no argument for it?
The heuristic they use is something along the lines of "only accept edits that are grammar fixes, equivalent thereof, or rewordings". Content changes without the authors consent are considered poor form.
