Im not saying there's any credibility to the V8 rumors, but you can't draw an inference either way from that article. That piece is speaking very specifically about the HSC concept car. As we all know, that car had a 3.5L V6 engine. Whether or not the HSC will make it into production, and what powerplant it would have if it did, is all still unknown.
ANY talk about the ACTUAL HSC prototype, however, is going to reference that 3.5L 300HP V6 engine. It's just a concept car for now...