Your view of Minor vs. Happersett is flawed. The Court does not define NBC, but rather one aspect of it as applicable to Virginia Minor, and says
As to this class there have been doubts, but never as to the first. For the purposes of this case it is not necessary to solve these doubts.Got it? The court did not resolve these doubts since they were irrelevant to the case. So no, the case did not define NBC.
And they were. What part of UNANIMOUS DECISION do you NOT understand?? Do you think it was NOT a unanimous decision in Minor??