“Not to say anything about quinoa specifically, but as is well known, the sephardim frequently engage in elaborate rituals to ensure that their rice is chometz-free. “
It seems to me that quinoa should also be checked 3 times, the same way Sephardim check rice. There are types of rice that KFP for Sephardim (see JSOR guide to Pesah), but that only means that chametz products were not added to the rice. The rice still needs to be checked. Same thing here.