That is only correct for some cars, When your car was new, it was equipped with a ground cable that was in a Y shape, one end connected near the bracket of the transmission mount (foundation) and one end on the body sheet metal, the last end was the terminal.
It is a very good system and causes full amps to be transferred to the starter windings. While the body can be dodgy as it is quite old too, rust/weld etc.
