I can imagine having to render fewer sections of grass, fewer tree's, and fewer billboards (which means fewer textures all together) can allow for more of those resources to be allocated to other things, which is where I think the frame increase comes from.
Considering that this build isn't 30fps faster, I don't think we should be looking for major changes to increase frame rate, rather, minor changes to stabilize it (which, looking at screens and comparing the two versions, is what happened).
Right?