As I understand it, it's more about how long the food stays in the "
Danger Zone".
Kidding aside, from Wikipedia: "The temperature range in which food-borne
bacteria can grow is known as the
danger zone. Food safety agencies, such as the United States'
Food Safety and Inspection Service (FSiIS), define the danger zone as roughly 5 to 63 °C (41 to 145 °F).[1][2][3] The FSIS stipulates that
potentially hazardous food should not be stored at temperatures in this range in order to prevent
foodborne illness (for example, a refrigerator's temperature must be kept below 4 °C (40 °F)[4]), and that food that remains in this zone for more than two hours should not be consumed.[5] Foodborne microorganisms grow much faster in the middle of the zone, at temperatures between 21 and 47 °C (70 and 117 °F).[6] "
So this can affect things differently. Soups, for example, like to stay hot, so there are actually giant plastic spikes filled with water that get frozen that professional kitchens use to cool down soups super-quick.
Basically, if you seal some food with plastic wrap and put it in the 'fridge, the seal also helps keep in the heat, so it's in the Danger Zone for longer, which can result in bacterial formation.