That's why one is called the golden master and the other is a master, not much to confuse. The "golden" is what signifies the unique meaning, i.e. the final, that both are masters is an accurate takeaway.

Main (or most any other common primary branch name) can have equally trivial confusions that are not actual problems. The endless debates about branch names didn't come about because people were so confused we needed something else to stop the madness, they came about because people were convinced they could find a problem to need to fix. Any of these branch names work equally fine, it really doesn't matter and there is no deeper logic needed to justify why we switched.