<p>"We are regrettaby unable to make a decision on your application to Columbia University.Although notices of missing material were sent to you via both e-mail and conventional mail,required documents were still absent from your folder as of March 29,2007."</p>
<p>This does not say that she got rejected though. None of the three application outcome actually occured: acceptance, rejection or waitlist. You can't derive from this sentence that they actually counted their applications. If you get an official statement from CU which declares that they counted them, then I'll believe you.
Just hypothetically: Withdrawals occur at any college, so CU wouldn't get an advantage over any other school. If what you say is really true then it'll probably be common practice among top colleges. TBH, admit rates belie the truth depending on what kind of student you are. If you're not a URM, legacy, development case or recruited athelete, chances are that the 8.9% are way too optimistic. Also if you apply during RD and are a needy international, you can only dream about a 8.9% chance. IMO, the 8.9% make CU sound easier to get into than it is for the vast majority of non-hooked kids.</p>