This is Steam, do they even have an ability to control that?
Besides, why do you care? It works and that's enough.
Steam is nothing special as a developer you have the control over where files are located in your own directory structure.
It looks like COD went with an archive format for their files now which allows for better compression on the archived files. This will in turn have a faster load from the disc with perhaps a trade of in the decompression step of those files in the archive. The massive FF files seem to be the archive files. And it seems like they made a single archive per location which means you dont have to jump through the directory structure to load the files for a level. This is offcourse all speculation on my part