That's true. One quick side note though: BTRFS actually had a fairly long "draft period" (multiple years) of design. I have no clue how long that was on ZFS. I just know that the original author mentioned that somewhere.
I am the guy who asked the LZJB question. To summarize my recollection, formal design work on ZFS started in 2001 when Matthew Ahrens started working at Sun. Jeff Bonwick had promised Matthew Ahrens a job at Sun making a filesystem a 6 months to a year before then when Matt was still in college. I am sure that both Jeff and Matt had some thoughts on it during that time, but there was no formal effort until Matt's employment started.
http://m.youtube.com/watch?v=dcV2PaMTAJ4
I am the guy who asked the LZJB question. To summarize my recollection, formal design work on ZFS started in 2001 when Matthew Ahrens started working at Sun. Jeff Bonwick had promised Matthew Ahrens a job at Sun making a filesystem a 6 months to a year before then when Matt was still in college. I am sure that both Jeff and Matt had some thoughts on it during that time, but there was no formal effort until Matt's employment started.