Polynesian plural form
The "plural" string isn't an English plural:
This leads to clunk like
The Magnificent Polynesian The Worthless Americans ...
I can't find any evidence that the noun "Polynesian" has unusual pluralisation, so I think it's just an oversight.
It's been like this since the nation was added in r12494, PR#30939. The file attached to the mailing list that apparently came from the forum is like this. No rationale there.