Yeah, that could be. I don't know if Harry's safe from torture though. But, didn't the Death Eaters (or at least the ones closest to Voldemort) know? In GoF, doesn't he (Voldemort) say something like... why would his believers pretend not to believe when they knew the steps he took to prevent himself from dying a mortal death? That would imply that they knew about the Horcruxes. To me, at least.