The East-West ship factor did not seem to come into play much this weekend. Some possible explanations:

Eastern trainers are learning.

Del Mar is much closer to the ocean than Santa Anita and hence experiences more moderate temperatures.

A warm autumn on the East Coast meant less disparity in temperatures.

Since the meet at Del Mar is just starting, even Santa Anita horses had to ship and adapt. In this regard, it is perhaps notable that Peter Miller stables at San Luis Rey Downs, so many of his horses were already in San Diego County. I don't know when they would have vanned to Del Mar.