Knowing the approximate file sizes and number of files in a directory, especially with further context of overall directory structure can allow someone to guess what the content is with high probability if the files are "well known". Consider a directory containing pirated episodes of a tv show, organized with a subdirectory per season. "Scene releases" tend to have one a few possible approximate file sizes, and depending on how much padding, it may be enough information to identify a set of files as all being scene releases of the same show. Many other examples like this - anything "popular" that's will have a fingerprint of extracted file sizes.