I dont think you can "spot reduce" any area right? Biking definately strengthens low back and probably stomach muscles- when I injured my hip, I had to strengthen these muscles to support it because my hip muscle/s werent coping so great, and my physio had me biking. Same with my mum who has lower back problems. So if you lose fat by biking, and build muscle there by biking, then your lower stomach will probably look better (but other parts of your body will probably as well, because you have lost fat overall).
I say this without reading Amanda's article