The way I see it, the required amount of posts rule is to make sure that person applying is active. I believe that the admins could also go back and check those previous posts to see how you act on the forums and that might help them decide whether or not to accept the app. Now, I can't be sure as I haven't been here long enough, but thats just the way that I see it or perhaps, the way I would run it.
Getting ten posts legitimately isn't that hard. Just find a thread that intrests you and give your two cents. If someone made a posing thread then go offer your support by telling them how good their poses are or giving them tips on how to improve.