because he does not know what he is talking about. You can have a volt meter in any car, and all modern cars have a alternator warning light regardless of voltmeter. The alternator actually requires the light to switch itself on.
but if it is wired for a voltmeter it would be providing constant 12v to the light instead of a guage, so his car (ae82 which has a light not guage) might have a alternator that is intended for use with a volt meter.
i do not no if they run different systems and all the specifics so i apologise if im wrong, just the way i take it is some alternators have a switch or similar that turns on/off when the voltage is below or above a certain point which then goes to the batt. light, and those with volt meters just have the voltage displayed.