I don't think this can be said enough that a two player AP would not go over well with a set of judges.
First, it has an inanely low level of difficulty in terms of keeping a plot balanced and moving. While this can happen with an incredibly large group, the two player group is worse. In terms of judging, the GM cannot show off their skills at handling a larger group with a number of different player agendas that one must keep balanced.
Second, you don't get a good feel for how players interact with one another and how the players interact with the GM. In Arcadia Signal, there was a lot of one-on-one RPing because Cody and Jason would separate. With a multiple player group, when groups separate there is still an added dynamic because players interact with each other more still than strictly interacting with the GM. Basically, it's the difference between when you played RPGs when you were 12 and strapped howitzers on your AutoDuel car and big-boy gaming.
Third, you have a lot of dead space in terms of "what do you want to do?" "I don't know, what do you want to do?" "Fine, we'll do this." In two player games, there is a greater opportunity for one player to dominate the field of play without much input from the other player. Even in well played two-player games this happens. If you don't believe me, listen to Arcadia Signal again. In terms of judging, a multiple player game allows the judges to hear how the GM deals with PC-group agendas as well as individual agendas.
