Booking FD so early you have first choice in resort availability, plus knowing you already have your FD res in place (with $200 down and don't have to pay until 45 days prior) while everyone else is dying with speculation of if they will even offer it or not = eases a lot of people's FD anxiety.
Also last year the DISers who booked the FD BB reported they got the Basic
DDP in Value resorts instead of the QSDP, so that was a plus too.