The data was literally duplicated, it was primarily textures and models. The reasoning was to reduce loading times for players with harddrives because the seek head wouldn’t have to move as much to find the data it was looking for, but because the textures and models are streamed in at the same time as the level was being generated (a slow process regardless of the storage medium) the duplicate data wasn’t actually helping that much.

Unsure if you couldn’t deduplicate it lol, maybe Steam would complain because your files are altered?