If a reported bug isn't really a "bug", it can be closed as such. However, by placing known issues on the bug tracker, it allows the devs to go to just one place to see what needs to be worked on.
The current "beta" thread is currently sitting at 21 pages, most of which is fluff and not bug related. Now, as a dev, what would you rather have. A specific bug tracker that has everything in one place, or have to wade through 21 pages of BS to find issues?
I know which one I'd pick, and it's not a 21 page thread.