I was about to tell you how wrong you are and that you had completely misunderstood sparse files. I'm happy to report that I've now corrected my own misunderstanding instead. Your article reads correctly when I don't read it with my own incorrect preconceptions. The benchmark and sparse checker utilities are appreciated! fallocate -d is a nice trick too.
Comments on What are sparse files and how to tell if a file is stored sparsely
Daniel, there's a typo in the table: "Unupported".
Thank you for the article! You write “The file is sparse (or compressed by the file system!) if the resulting number is lower than the sector allocation count.”. Do you have an example of a file system where this is the case? Btrfs doesn’t do it for backwards compatibility reasons: https://btrfs.wiki.kernel.org/index.php/Compression#Why_does_not_du_report_the_compressed_size.3F