FreeBSD-EN-07:05.freebsd-update

ERRATA NOTICESでてました。今回の対象は6.2-RELEASE

On the i386 platform, if a system is running a kernel built from the
default SMP kernel configuration, and this kernel is installed somewhere
other than /boot/SMP/kernel, the FreeBSD Update client will not download
and install updates for it.

なるほど、てっきり仕様かと思っていました。:-)
freebsd-updateで更新できるのですが、2回やる必要があります。

a) i386 systems:

It is possible that past kernel updates have not been downloaded and
installed by FreeBSD Update. To ensure that all available updates have
been installed, run FreeBSD Update twice; first to download and install
an updated FreeBSD Update client, and second to download and install any
updates which were missed earlier.