Actually, the explanation is much simpler than that.
Last year, around this time, Disney did the big explosion of choices for online check-in. EVERY longhouse was listed (even Hawaii and Tonga, for all the good they do most Poly bookings!). "Guaranteed" connecting rooms were a choice! You name it, it was a choice. It was kinda bananas. Many choices were also physically impossible. This happened at every resort.
Someone realized that this was nuts and got IT to "roll back" the choices. But IT did not roll back to what was previously offered. They rolled back, in most instances, to ~5 options -- and at Poly, this ended up being Upper, Ground, Balcony, Patio, and to get a 5th, they left the first longhouse in the alpha order of longhouses.
I actually don't think more thought went into it than that. A comes first.