https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=221795:
The `zpool list` section of the zpool(8) manpage says that the default list of
displayed properties is as below:
The default list is name, size, used, available, fragmentation, expandsize,
capacity, health, altroot.
This does not seem to be the case. In fact:
    # zpool list
    NAME   SIZE  ALLOC   FREE  EXPANDSZ   FRAG    CAP  DEDUP  HEALTH  ALTROOT
    tank  10.9T  6.05T  4.83T         -    29%    55%  1.00x  ONLINE  -
The Properties section of the same manpage includes the `used` property, but
this seems not to be recognised:
    # zpool list -o used
    bad property list: invalid property 'used'
    usage:
    [...]
    #
The usage message produced here indeed doesn't include `used`.