it isn't just post count that allows someone to start authenticating.
The 500-post count requirement is in effect to allow unproven posters to prove themselves by demonstrating their knowledge.
And do you not think that if someone posted misinformation one of the "real" experts wouldn't call them out on it? You'd better believe it!! It happens all the time, whether the poster incorrectly authenticates or if it's in another subforum and the advice given is bad. They're promptly corrected and sometimes, even not-so-nicely advised not to give bad information.
Here's one example where a newbie was called on posting misinformation, called on it and got defensive. It starts here and the correction continues for several posts:
http://forum.purseblog.com/coach-shopping/authenticate-this-coach-855067-315.html#post26924339
there are reasons for rules and it's not a conspiracy to allow fakes to be sold by special snowflakes!