running "login username" from a shell logs a user out.
I have verified this to be true on a test machine with a stock 6.0 install. Also it disconnects if you enter login by itself with no arguments. Proper behavior you would get a prompt asking for username.
The login program from a shell is only intended to be run as "exec login username". Even then the fact login does anything is more V7 tradition than anything intended.
that's what login should do. i am suprized it works too.