I just looked on Google Earth, and Brandon is indeed on the main road between Corsicana and Hillsboro. Corsicana and Hillsboro are only about 40 miles apart.
It does look really flat around there. Perhaps Bearshouse misread “Hill County” as “Hill Country”.
I’m familiar with the area, it’s basically flat. The Hill Country is further West than Hillsboro. I would consider Hillsboro in the foothills of the Hill Country. I lived in Texas for about 36 years and have been through both Towns although not from Hillsboro to Corsicana.
IH-35 is the “dividing line” for the most part. East of IH-35 the soil is dark almost gumbo mixture with some clay, West gets into Limestone and that’s where the Hill Country starts but further West than Hillsboro.