I suspect it is ground conductivity at the receiving site, not the transmitting site, that is the problem.
In the case of North Georgia, it is bad conductivity of the entire zone.
In an area of very good conductivity - Lubbock, TX - I had no problem receiving it with a five foot loop during the day.
Reception like that during the daytime at that distance is an anomaly and might be attributed to daytime skywave at times. From experience, using a professional communications receiver and loop, reception in Birmingham, AL is not consistent... and that's a lot closer (it is just outside the 0.1 mV/m contour and very, very weak if receivable)
I did this at different times of the year. Of course reception of that type is subject to deep, long lasting fades, but WSB was definitely there. I heard multiple ID's and Atlanta commercials.
If you had deep fades, that was daytime skywave.
As another poster mentioned, the bad groundwave coverage of WSB can be seen in how close in the skywave/groundwave cancellation can occur. At night, they are also seriously ripped up by the much more powerful RCR from Caracas.