Their coloring isn't listed as a variety as it is with the cockers (black variety, ASCOB variety, Parti variety). Instead it's described as a pattern, which I guess makes it more acceptable to purists:
Dappled dachshunds - The dapple (merle) pattern is expressed as lighter-colored areas contrasting with the darker base color, which may be any acceptable color. Neither the light nor the dark color should predominate. Nose and nails are the same as for one- and two-colored Dachshunds. Partial or wholly blue (wall) eyes are as acceptable as dark eyes. A large area of white on the chest of a dapple is permissible.
American Kennel Club - Dachshund
Again, it comes down to the recognition by the parent club that a variety exists within the breed. And, this is just my opinion only, it's the refusal of the parent club to acknowledge that the coloring exists naturally within it's lines is the reason for this divide.
Not to mention that AKC standards have always been about the "look" of the pup and rarely about the health of the breed. You can show and champion a yorkie that has LP or liver shunts in the line, but not a healthy one with white markings. That makes no sense to me when their mission statement says:
Founded in 1884, the AKC® and its affiliated organizations advocate for the purebred dog as a family companion,
advance canine health and well-being, work to protect the rights of all dog owners and promote responsible dog ownership.
I just don't get it...