Actually, I should have phrased that a bit better. I don't know the proportion of food:light, but these anemones do obtain more energy hetertrophically (by comparison) than some other host anemones. Some species can still do well in lower light with plenty of food. They also may do well with higher light and proportionally less food. However, I don't think it is quite to the anemone's best interests to lower the overall amount of food. They will do best with heavy feedings and good light.
As far as a MH only anemone, it would really only depend upon the species. I think the only one that would really NEED MH would be, say, S. gigantea. The other two species, S. haddoni and S. mertensii, can be kept in less. S. haddoni has even been kept many times under NO fluorescent tubes. IME, good feeding in addition to good light encourages the best in these anemones, as well as many others (especially other Stichodactylids).