The hold South (or North or whatever) is to account for a holding fix that isn't at the navaid ie a bearing/radial+DME distance. You would still be on the specified bearing/radial but could hold in one of two possible directions. For example,
"Hold south of the xyz 180 radial 10 dme fix..." or
"Hold north of the xyz 180 radial 10 dme fix..."
Draw the two and see the difference. Remember, to hols south of somewhere on its 180 radial the inbound track must be 360. Vica versa for hold north.