The speed passion sportsman v2 are actually motors from a company called Feigao. They make decent quality, low cost motors.
http://www.feigao.com/sdp/85838/4/pd..._road_car.html
They don't put a lot of info on their website, but I think it would be safe to say that the rotors are indeed sintered. Feigao's other 540 motors all have sintered rotors, and this one is certainly not at the bottom of their product list.
Jon