Why do the sorting optimizations create fragments?
The sorting optimizations will move all the data to the beginning of the harddisk. But there may be some unmovable files in the way. Instead of leaving gaps (if a file doesn’t fit between the last file and the unmovable file), the program will “wrap around” the unmovable files by splitting regular files into fragments. This may seem strange for a defragmenter, but the fragments are aligned and the impact on performance is therefore very small. Gaps however would make all the files above the gaps slower, because they would then be placed at a slightly slower part of the harddisk than they need to be. The fragments look terrible on the screen and in the statistics, but are there to make your harddisk faster!
