The reason for high download size of the update

This is just a speculation but the most probable reason that I can think of is that they preloaded the rest of the hidden mountain and the hutuo region alongside the imperial palace. What led me to this conclusion is the fact that I got loading screens from both Mohist hill and Hutuo while hanging around the northern edge of qinghe.

They did the same thing during the Hexi update, they preloaded the entire hexi region alongside the first part of Hidden mountain region.