The OP is correct. I just called for a seating at Sci Fi for four at a normal lunch time. The only way I could get that was to have our party split up in two cars, two people per car. I could get a seating for 2:30 for all four of us in one car, though.
OP - the person you spoke to is not at the restaurant. You can show up with your entire party and request to be seated all in one car. However, you will probably have to wait as a walk up if you are even allowed to change your reservation at that point.
The other posters are also correct - the cars seat six, with some seating only four.