I have taken a 75 gallon and a 29 gallon down to 2 inches of water above 2 inches of gravel to move tanks in the past. The fish are fine. As long as the filter media and gravel stays wet your good bacteria should be find. The important thing is to get within acceptable range with the nitrites before permanent damage to your fish. You have to understand that some of the information you get is conflicting because not enough questions were asked, and particulars given before giving the advice. You were picking up the general rule without seeing the when this happens scenarios. And then there are the people who do things their own way who have had success, that may not necessarily work for you. Advice is just that, as with all life there are no rules or norms that are set in stone. Fishkeeping practices have evolved though the trial and error process and it continues to improve though the care and attention of dedicated people who genuinely care about the health and well being of their fish. So take all advice with a grain of salt and try to look for a consensus before taking action.