I think there are two factors in this decision. First, they don't have the ability to stop the fire. It's going where it wants in places that haven't burned. Second, weather. I think these bursts of cooler weather are going to bring windy conditions. It will be out of the south as usual, then this weekend it will pick up and turn out of the southwest. The first little burst of santa anas has been mostly taken out of the forecast, leaving just 9/28 for the next santa ana change in wind direction.
So, in short, the fire is to Wrightwood's west, and the wind will be out of that general direction for a little while.