I agree. My son had too much on his plate to bother with yet more paperwork and chasing down unnecessary recommendations; it didn't hurt him.
Remember that NHS is a derivative organization: By that, I mean NHS is pretty much meaningless in itself, the high grades and community service work required to get in stand on their own merits. If Brown is sufficiently impressed with your grades and community service projects, do you think whether or not you were "vetted" by NHS means anything?