Because it's wrong. The FAQ itself states that the benefits of registration are prima facie evidence and statutory damages. You can still litigate, you just need to provide alternate evidence and you don't get to claim statutory damages (you have to prove the damages you're claiming).
Perhaps you should reference title 17 of the U.S. Code. Section 411 deals with registration and civil infringement actions. Specifically 17 USC § 411 (a) says:
"Except for an action brought for a violation of the rights of the author under section 106A (a), and subject to the provisions of subsection (b), [1] no civil action for infringement of the copyright in any United States work shall be instituted until preregistration or registration of the copyright claim has been made in accordance with this title. "
