That has to be the most rediculous thing I've ever heard. I lost 48 pounds in 14 weeks the first time I dieted down and I don't remember my stomach growling. Guess the fat loss was in my head. In fact I rarely notice my stomach growling ever. Also liquid moving through the intestines is not gas, that'd be diarrhea my friend.
My guess is that whoever you heard this from is implying that if you're stomach is growling then it is empty therefore you are burning stored calories. I'd say that would be obvious. But if it means that when your stomach growls it is some tell-tale signal of your body switching to fat burning mode then someone has been smoking something they shouldn't be.