Can't find the post (someone else might be able to direct you) - but it's related to a certain ticket someone sent to Nutaku regarding the free weapon/eidolon expansions that we didn't get (whilst DMM did). Their reply was among the lines of "Nutaku Kamihime is their own original version, that doesn't follow DMM". Probably just a convenient excuse in the long run.
Susanoo's and L. Tsukuyomi's light/dark resist up seem to work fine. At least, they apply the buff, haven't tested if they lower the damage.