I suspect the lower temperatures represent situations, near term use and foods that are more susceptible to harboring food poisoning. Lower temperatures often 'deactivate' microbes, beat them around the head and shoulders and lower their populations to safe levels. This is okay short term but, inevitably, some of the bacteria will still be active. If the food is consumed quickly this small number isn't a problem. Whereas, if the food is a type that promotes easy growth and the food is not consumed in the short term those stunned bacteria start to multiply.