A black sexlink hen is a cross of a RIR and a Barred Rock, both single combed breeds. There are no pea combed birds in those breeds. I think I'd ask what else they have on that farm, if I was you. Trust me, I know my breeds pretty well. They do not get spurs till they are about 7-8 months old. Both sexes have a bump there, though.
There is not a black Rhode Island Red. There are darker ones and lighter ones, but they are not black. I have breeder quality RIRS that are quite dark, but they are definitely not black. Where did you find that information?
It's possible a pea combed breed was in the lineage of the breeder birds they used, but not in any breeds that make up the black and red sexlinks.