IMHO, a single carrier status is irrelevant to USAPA's responsibility and right to finish the MB process that was contractually agreed to. If USAPA loses their rights and responsibilities under MB, simply because of single carrier status, then the APA and the company are wasting time by asking USAPA to agree. And even worse, the Congress of the United States wasted their time creating a law that would never be implemented. The APA is making up a very lengthy FUD piece to manipulate the negotiations with the hopes of getting USAPA to agree to a change to the MOU... to abandon its rights and responsibilities under MB.
Think ALPA/TWA. If APA can strong arm the legal representative into doing something stupid then the APA wins and can't be sued. This time APA's opponent isn't ALPA drooling over the possibility of getting everyone back into the mothership. YMMV.