Probably 99% of the chicken owner population are not members of the APA an are free to call an sell there birds under any name they see fit. Unless they are claming to meet standard or be show show stock the it does not matter.
Yes, anyone can call their chickens anything they want. But there have to be recognized standards for a pure breed. A person can call a Rhode Island Red a Barred Rock if they like, but that chicken will not be recognized by an organization as a Barred Rock.
I can call a black and yellow dog a Labrador Retriever, but there is no standard for a black and yellow Labrador Retriever.