That the dog does not carry yellow. I think.

On mine, it doesn't go away, but you can't see it unless you are really looking for it. When my chocolate girls shed, if I pull out fur by their shoulders, it is tipped in white also. Many of mine are not pure for chocolate, and still have "the ring". I do have lovely coats on most of my chocolates with this. I do have one nutty girl, but most of my chocolates are kind dogs, and maybe a bit dramatic and starving all of the time!

There is nothing wrong w/ your chocolate having white at the base of the hair. Some blacks will have this as well as yellows, you just can't see it in the yellows.
When you have a dog that is shedding out its coat you will be able to see it on the dark dogs but other wise it will be hidden. Mary Roslin Williams said in her book "Advanced Labrador Breeding" something like the best coat has white at the base of the hair.

So no worries with your dog.

My blacks have the white hairs too and Bolo pads.