Has the AKC ever accepted historical dogs, with flawed or open pedigrees?
Yes, but only on a case by case basis, usually with regard to dogs historical in some way to a breed or from a time where complete DNA is impossible to acquire. The AKC understands that the founders of just about any breed include mixes and that old records can be incomplete or erroneous, but it does make sense that they will not accept dogs with a clear history showing they are not purebred. Only one Chinook, Northdown Nugget (1989-2003), whose pedigree is questionable, was examined by the AKC on an individual basis and allowed to be included as a historical Chinook. Nugget was never part of a Chinook crossbreeding program. Another dog that people seem confused about it is Howlin Hills Genesee, registered to Amanda Bays. She was submitted to the AKC as a purebred and later confirmed as purebred through DNA, but had to go through the COA in order to correct her pedigree in the UKC where she was incorrectly listed as a cross.