jails jail console TERM variable

[GilGalaad]

Hello guys,
I have been using jail for quite a lot of time (since 10.3, currently on 11.2) without any real issue except this strange one (which is not a real problem, just a strange behaviour).

My jail.conf

path = "/store/jail/$name";
transmission {
        host = "inherit";
        ip4 = "inherit";
        ip6 = "disable";
        exec.start = "/bin/sh /usr/sbin/service transmission start";
        exec.stop = "/bin/sh /usr/sbin/service transmission stop";
        exec.clean;
        mount.devfs;
        persist;
}

When i log into jail console using service jail console transmission, i get the following environment

USER=root
LOGNAME=root
TERM=su
HOME=/root
SHELL=/bin/csh
BLOCKSIZE=K
MAIL=/var/mail/root
MM_CHARSET=UTF-8
LANG=en_US.UTF-8
PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/root/bin
HOSTTYPE=FreeBSD
VENDOR=amd
OSTYPE=FreeBSD
MACHTYPE=x86_64
SHLVL=1
PWD=/root
GROUP=wheel
HOST=DarkSun
EDITOR=vi
PAGER=more

that is perfectly fine except for the TERM variable, that is totally wrong, and confuses editors like vi or nano (and everything based on display size or ncurses, too), making them impossible to use. Not a real problem, since normally I edit jail files from the host and not within the jail itself.

But the strange thing is that if I look into /etc/rc.d/jail, console subcommand is basically translated into jexec transmission login -f root.
If I run manually jexec transmission login -f root, of course i jump into the same jail console, but this time

...
TERM=xterm
...

and everything works correctly.

Am I missing something? Did I run into a bug?
Thank you.

P.s. As side note, I can't fully understand exec.clean directive, because it seems uneffective, but I will probably ask that in another thread.