I have several systems that were running 11.0-p1 (RELEASE) and needed to update them to the latest security patches. Freebsd-update brought down the updates and when they were installed it said nothing about rebooting so I didn't.
FreeBSD sermons 11.0-RELEASE-p1 FreeBSD 11.0-RELEASE-p1 #0 r306420: Thu Sep 29 01:43:23 UTC 2016 firstname.lastname@example.org:/usr/obj/usr/src/sys/GENERIC amd64
Once I rebooted the system, uname showed -p2:
FreeBSD master 11.0-RELEASE-p2 FreeBSD 11.0-RELEASE-p2 #0: Mon Oct 24 06:55:27 UTC 2016 email@example.com:/usr/obj/usr/src/sys/GENERIC amd64
Apparently a reboot was required after the freebsd-update install and it should have told me that was the case.