I remember an Encyclopedia Brown mystery where it was solved by his side-kick Sally because of a similar question.
A man was disguised as a woman and they had to find which one in a restaurant. Turns out, a woman in supposed to see and be seen, and thus be facing the front. The man is "the protector" and will be closer to doors. The "woman" was seated in a man's position.
I know, it never made sense to me either, because I could think of so many arrangements! But Sally solved it because she knew manners and Encyclopedia Brown did not.
I like to sit with my back to the wall if possible, and not be "trapped." But I will sit just about anywhere if the food is good and the price right!