Subsection (d) simply outlines the rules for a vote on the master.
Subsection (b) States that an agreement will become binding if approved by a majority of voters, and outlines how local unions might be able to witndraw from the master agreement. Then it goes on to outline what happens if the master passes, but a supplemental does not. The steps outlined in subsection (b) pertain only to supplementals and riders that were rejected, not to the master.
I have to admit I'm not sure about the meaning of this paragraph in subsection (b)
"When a master agreement negotiated under the provi‑ sions of this Article provides for a reopener and re‑nego‑ tiation, or is voluntarily reopened during its stated term, the above voting procedure shall apply to ratifcation of the new terms, if any, and Section 2(d) shall apply to strike votes."