Not an expert, but the donating (and/or bloodletting) is scheduled frequently enough to keep their iron from deviating too high above normal, and someone receiv

Not an expert, but the donating (and/or bloodletting) is scheduled frequently enough to keep their iron from deviating too high above normal, and someone receiving a transfusion is typically going to be low on blood. Put 'em together, and I'd be surprised if a hemochromatosis transfusion could be a problem for anyone who doesn't themselves have hemochromatosis. But yeah, this does seem like a really mutually beneficial arrangement. They need to lose some blood either way, might as well put it to use.