I have reason to believe they also can input data beyond the basics. A few years back, was coming through immigration in DEN. Had been out of the country in the past 30 days, so had to declare everything. However, this trip was for a friend's wedding, and literally the only thing I was bringing back was a pair of maracas from the wedding, total value $2.
I'd stopped in the restrooms on the way down, and was literally the last person going through immigration. The CSP officer took a look at my declaration form and said "WHAT?" - I mimed shaking maracas, said I had to declare them as I'd used my exemption in the last 30 days. He burst out laughing and waved me out, stating "get out of here!" As I left, he started typing furiously.
Ever since then, most of the time I come through immigration, the CSP officials read my data and then start chatting about what I do, but usually very light hearted and with a smile. A couple have chuckled while looking at the screen. I'm convinced that the DEN CSP put something in my record to indicate I'm need only the lowest level of scruitiny.
Of course, now that I have Global Entry, don't get to watch the expression change anymore when I go through, but I will say my GE application was mighty expedited as well.