I'm no expert by any means, but I would say that the new roots develop off of root buds, not off of existing feeder or water roots. So, if you replant a neck, it shouldn't matter if it shows any root hairs or not, it most likely will bud out new roots and continue to grow - assuming conditions are right, such as moisture, etc.
Just my .02 worth from a plant background, though not a specialization in ginseng plants.
Will be interesting to see folks' experiences over the next several years with this! k