Not only is the Antarctic circumnavigation a shorter distance on a RE than the distance circumnavigation around a RE (or 21,600 miles), but it is known that the winds are anomalously fast in the Southern Hemisphere. A number of quotes can be found which suggest that the winds in the South are of an anomalous nature as compared to the North. They become more anomalous as you travel Southward:
Not anomalous, just different. Given the uneven heating mentioned in your BBC quote and the fact that, except for the southern part of South America and New Zealand, there is little to no land mass between 40 degrees and 65 degrees south latitude to get in the way, one should expect the prevailing winds in the south to be significantly faster than in the north.