Here's a few of my observations for my area. I never waste my time setting for a storm wind, which is the from the NE here. I used to but just doesn't produce enough to waste my energy doing so. You will hardly see any coyote movement the day of storm front here. Most hunting is done a day or two ahead of the front. All of my sets are set for the predominant wind for the winter season which is NW, W for my area. I always use a backing whether it be a cow chip, grass tuft, weed, or bush in a flat area with at least one smell (gland lure, urine, curiosity lure) outside of the hole if it's a dirt hole set to catch the air currents.
I did have a set this year that I set in front of a knoll about 3 feet high instead of in a flat area. I believe the air currents would make the scent swirl and the coyotes worked it from behind every time. I've had fox work the back side of set a lot when the wind was from the opposite direction but if the wind is moving in the right direction they'll be waiting for you. Folks, animals don't know or reason the front from the back. So the direction the air is moving the scent definitely has an affect on their approach. There was a study done showing that 9 out of 10 canines will approach a set from the down wind side. So yes, there are some that will for what ever reason approach from the back but it's best use the air in your favor. Some may say well the wind comes from all directions during the day. True, but know what direction the wind blows during night. The breeze will generally reduce during the night and be consistent. The heavier cool air will also keep the smell lower.
Notice I said approach from the down wind side. A very seasoned trapper and tester of scents notes that most of the time they approach from the down wind side, take a whiff of the smell and then proceed to step around to the back side. So if you missed on the approach this may explain why the back side is dug out if the animal is interested enough in the smell. It may just simply move on as well.