She isn't a clay court specialist but she found her groove on the clay. You can tell something clicked in CHarleston that wasn't there before. She used to play a good point, nice and forceful and aggressive, then she would play a few games of being passive, push the ball instead of hitting through it. That was how the players could move her around. Thats how she got those little nagging injuries. Once she got over everything anf then just played like she wanted to, she started with better results. It just happen that is occured on clay.
And if Venus isn't an all court player, I don't know who is. Her obvious best surface is grass and the fast USO hardcourt, but most all court players have a favorite surface where they thrive. Evert was clay, Serena is definitely hardcourt, and Justine is clay, and Kim is indoors and harcourts. Just my opinion.