For anyone who ends up searching for this and might need the help...
Some cars have dual filement bulbs and some have single filement bulbs. My car for example, with factory headlights (1998 Civic), uses dual filement bulbs. That means my high beam and low beam come from the same bulb. My sister's car, with factory headlights (1998 Integra), uses single filement bulbs. Her high beams are seperate from the low beams. A car doesn't have to have seperate housing for each bulb of course though. Some cars, a 1997 Eclipse for example, use single filement bulbs, but they both get installed into the same headlight.