The very round shape of the Sun

At http://phys.org/print264350481.html … we have a post on the shape of the Sun, and its roundness. . The Sun rotates every 28 days and therefore, it is claimed, it should be slightly flattened – but it's virtually a perfect sphere. This suggests, they say, that subsurfaces forces such as solar magnetism, or turbulence (or possibly even electricity?) may be a more powerful influence than than expected. The paper is published in Science Express – whilst everyhthing else about the Sun appears to vary, such as the sun spot cycle, the shaped does not. It is fixed – or so it seems (see www.sciencemag.org/content/early/2012/08/15/science.1223231)