If you look inside the pass. side handle you will notice that the lock cyl. turns the little push rod 90 deg. and flat cast into it blocks the button from being depressed to unlatch the door. My dad says this feature was so you enterd the cab from the curb, keeping you out of the busy muddy street. Model Ts only had a door on the pass. side for many years of early production, Probobly a leftover from the horse and buggy days.
