two Guardians, one cup Edit
This reversion asserts that Guardians of the Whills is "an organization, not a title." The former is certainly true, but the term is also used as a title on several pages in Wookieepeidia. (Three examples: the page May the Force be with you refers to "Guardian of the Whills Chirrut Îmwe"; the page Lightbow twice mentions a single Guardian, saying the bow "was built by a Guardian of the Whills... marking the Guardian's progression"; and the page Battle on Jedha mentions "two Guardians of the Whills.")
If such usage is correct, then the singular Guardian of the Whills is a meaningful term, and should be this article's title per Naming policy.