That's just the mutual masturbation area where you didn't care about the movie, you just needed some time alone with your date to get fingerblasted or get your pole tugged.
It was sloped at every drive-in I went to - so you'd see over the canteen/projection room.
Half the fun was queueing for burgers, chips (fries), and/or pizza, and coke between the two features. The other half was sneaking beer in. Then the other half was...... what was I talking about?