This is possibly because update-grub does not recognize the pc-bsd partition. I just installed PS-BSD on /dev/sda3 of a system which has Ubuntu 12.04 and Windows XP on it. Previously I had installed both FreeBSD and NetBSD installed in the same partition (slice ad0as3 in BSD terminology) and update-grub detected those systems, and grub.cfg was updated properly.
Note that older versions of Ubuntu weren't able to detect FreeBSD etc, but that was fixed a bit before 12.04.
This is possibly because update-grub does not recognize the pc-bsd partition. I just installed PS-BSD on /dev/sda3 of a system which has Ubuntu 12.04 and Windows XP on it. Previously I had installed both FreeBSD and NetBSD installed in the same partition (slice ad0as3 in BSD terminology) and update-grub detected those systems, and grub.cfg was updated properly.
Note that older versions of Ubuntu weren't able to detect FreeBSD etc, but that was fixed a bit before 12.04.