i agree that it's a glitch, but if there was to be a city added to p.s., BOS is the best choice. competitive transcon market, high O/D percentage, and a corporate base that can sustain high fares.
that being said, UA probably isn't too fond of how massport is throwing money left and right to foreign carriers (EK, CX, HU, JL). i don't have insight into load numbers for those flights, but it's probably not a bad sign that EK upgauged from a 772 to a 773.
i understand that the p.s. subfleet isn't big enough to simply add a city at this point - but i can dream!