Test takers report that MPEP Chapter 1800, PCT, is tested heavily on the Prometric Patent Bar Exam. Experiencing 3-4 questions on this topic is common and some test takers report as many as 10-15 questions (most likely some are beta questions).
A test taker reports a question about publication of a PCT application under PCT rules if the application is filed with the US receiving office and ONLY designates the US. Answer – MPEP 1803 (if the US is the only contracting state in an IA, IA will not be published at 18 months). Otherwise, the application is published 18 months from the priority date of the IA.
PCT 1803 Reservations Under the PCT Taken by the United States of America
[…]It has also declared that, as far as the United States of America is concerned, international publication is not required (PCT Article 64 (3)). Accordingly, under PCT Article 64(3)(b), if the United States is the only PCT Contracting State designated in an international application, the international application will not be published by the International Bureau (IB) at 18 months. Even though the United States Patent and Trademark Office has begun pre-grant publication under 35 U.S.C. 122(b), the United States has not removed its reservation under PCT Article 64(3) because not all United States patent applications are published. See 35 U.S.C. 122(b)(2). The application will, however, be published under 35 U.S.C. 122(b) if it enters the national stage in the United States. It will be published again if it is allowed to issue as a United States patent.