IME, when you get an X on the receipt, you fill out the normal landing card, and hand it to the immigration guy. You are then processed normally (except that you have head of line privileges at immigration). The importation of food or goods in excess of your exemption should not direct you to a special passport control desk. It should direct you to the customs desk that is after baggage claim but before the exit of the arrivals hall, where a determination will be made of your duty assessment and/or whether you get to keep your food.

As I recall from an experience last year at ORD with an X on my receipt (I exceeded my exemption), customs was aware I had GE because they thanked me for my honesty, and then decided the $5 in extra duty wasn't worth their hassle. But I can't recall if I still had my GE receipt at that point.