I think the helfrichi you are seeing are coming THROUGH Hawaii, not being collected in the Hawaiian chain itself. (Randall gives their distribution as "Polynesia except Hawaii).
I've only worked with one of these fish. It developed some odd scoliosis of its spine, but I'm not attributing that to the species of fish that it is. I was attracted to this fish at first due to its rarity and subtle colors, but as I think more about it, I prefer the decora species now - more colorful and more robust If you want a true Hawaiin species, you'd have to stick with magnifica, its the only species of the genus Nemateleotris recorded from there.
Jay Hemdal