pkg_add(8). Bug in handling the flag "automatic"?

[Aleksey Cheusov <cheusov%tut.by@localhost>]

According to the documentation pkg_add(8) should remove flag "automatic"
if the package already has it and -A option was not passed to pkg_add.

     -A      Mark package as installed automatically, as dependency of another
             package.  You can use
                   pkg_admin set automatic=YES
             to mark packages this way after installation, and
                   pkg_admin unset automatic
             to remove the mark.  If you pkg_add a package without specifying
             -A after it had already been automatically installed, the mark is
             removed.

Reality is the following

   asrock# pkg_info -Q automatic autoconf213
   yes
   asrock# pkg_add -UD /srv/pkgsrc_bin/NetBSD/x86_64/cache/All/autoconf213-2.13nb4.tgz
   pkg_add: Warning: package `autoconf213-2.13nb4' was built for a platform:
   pkg_add: NetBSD/x86_64 6.0 (pkg) vs. NetBSD/x86_64 6.1_STABLE (this host)
   autoconf213-2.13nb4: unregistering info file /usr/pkg/info/autoconf213.info
   autoconf213-2.13nb4: registering info file /usr/pkg/info/autoconf213.info
   asrock# pkg_info -Q automatic autoconf213
   yes
   asrock#

As you can see "automatic" is still here.
Am I doing something wrong?

-- 
Best regards, Aleksey Cheusov.