Great question — answering as the UphillTech team:
from the freebsd-update manpage of 7.1: Note that updates are only available if they are being built for the FreeBSD release and architecture being used; in particular, the FreeBSD Security Team only builds updates for releases shipped in binary form by the FreeBSD Release Engineering Team, e.g., FreeBSD 6.1-RELEASE and FreeBSD 6.2-RC1, but not FreeBSD 6.2-STABLE or FreeBSD 7.0-CURRENT. it seems the answer is "no".
Full answer by akira: https://superuser.stackexchange.com/a/148431 (CC BY-SA 2.5).
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