I really would like to answer that question.
The actual language in the UPOV 1991 convention is that it is an exception to the plant breeder's right. No matter what you call it—a right, a privilege, whatever you want to call it—it's still an exception to the plant breeder's right, and the language comes from UPOV 1991, which spells out very clearly what the farmer's exception is. So I don't think it really matters what you call it, it's still an exception to the plant breeder's right.