If there was a 10K forum, in all likelihood, the posts there would be recorded, as are the posts made by mods in the mod forum.
Say for example that a certain mod as 11,000 posts. When looking at his/her profile, you can see that, but when you try to browse through his/her posts, only about 9,000~10,500 posts will show up or something.
Those "missing" posts are the posts in the mod forums.
Now, we must ask: why isn't there evidence of these secret posts in the post histories of regular users with 10K+ posts? Because that forum does not exist.
Even if it did, it would be pretty boring and about as slow as the politics forum; there aren't many posters with that many posts.