sudo -u root sh on a root-locked FreeBSD

$ whoami
grahamperrin
$ sudo -u root sh
Password:
# whoami
root
# env
SUDO_COMMAND=/bin/sh
LOGNAME=root
LANG=en_US.UTF-8
XAUTHORITY=/home/grahamperrin/.Xauthority
MAIL=/var/mail/root
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/games:/usr/local/sbin:/usr/local/bin
SUDO_GID=1001
DISPLAY=unix:0.0
PWD=/usr/home/grahamperrin
TERM=xterm-256color
HOME=/root
USER=root
TZ=America/New_York
SHELL=/bin/csh
COLORTERM=truecolor
LANGUAGE=
SUDO_USER=grahamperrin
SUDO_UID=1001
# exit
$ sudo grep LOCKED /etc/master.passwd
root:*LOCKED*:0:0::0:0:Charlie &:/root:/bin/csh
$