When you enter the USA, it's common for the (immigration) official checking passports to ask questions about whether you're bringing any food etc. This is more common than being asked the same question after you've retrieved bags when you hand in your form or receipt at the customs exit. AFAIK they're all CBP officers with no separate immigration service and customs service as seems to be the case in many foreign countries. [However, in the days of the blue paper form, the immigrationer questioner would scribble on the form indicating if more questions or baggage (secondary) inspection are needed.]