Though spec bugs go the opposite way: if you discover an issue in the spec, then it is very difficult to change it because someone somewhere may have been - at the time correctly - relying on that behaviour.
Web developers can only rely on a spec bug if the browsers they test with actually implement that bug. So it still comes down to what browsers implement, not what the spec says.
Or, you could just be Google, and change your browser to work the way you want, and ignore all the pages breaking by insisting that the change is "within spec", giving a big middle finger to anyone that complains.
