Unix files have (at least) two sizes

Note that the ZFS choice will break tools that check for sparseness and assume it's a binary file. Off the top of my head, the most famous breakage was GNU grep ... 2.14?

It was GNU grep 2.13 and ZFS' behavior predates GNU grep 2.13 by many years. This was considered to be a bug in grep by the grep developers:

https://github.com/openzfs/zfs/issues/829

http://git.savannah.gnu.org/cgit/grep.git/commit/?id=2f0255e...