Even if we saw it coming, another movie could have won the DGA award. Also, BP/BD splits are rare. And, of all the Guild awards, the DGA holds the most weight. However, recently, the PGA has been a good indicator with 7 of the 10 past films in the last 10 years winning BP. The tie though sends things into a loop. But, you're right, it doesn't change much, but it does give Gravity a slight edge in winning BP since it seems highly likely it also wins BD.