misleading ZFS warning

Hello,

Doing this:

 zfs create  -b 4096 -o volmode=dev  -V 32G as1/dockerim/dsk.adocker

I've got

Warning: volblocksize (4096) is less than the default minimum block size (16384).
To reduce wasted space a volblocksize of 16384 is recommended.

While ashift=12 for this pool I can't understand am I really do something wrong and there will be "wasted space" or this is a misleading warning.

Can somebody enlight this?

-- 
Best regards,
 Anthony Pankov                         mailto:anthony.pankov@yahoo.com