What is a "typical partisan caucus" and how can the public be certain that this OPMA exception is not being used to subvert public's rights under OPMA?

According to a December 17, 2016 article "Jackson Council Spars with Resident Over Political Caucus Meeting," by Phil Stilton of the Shore News, local activists secretly videotaped the mayor and every member of the Jackson Township Council attending an unadvertised meeting at a law office.  Three members of the Township's Municipal Utilities Authority also reportedly attended.

When confronted with the evidence, Council President Rob Nixon claimed that the secret meeting was a "typical political caucus." Nixon is quoted as having said that: “The council separately from our political roles, we’re permitted to meet with anybody in a political context that we want to so long as township business is not discussed outside of that context.”

Nixon's comments correctly characterize the Appellate Division's holding in Mountain Hill, LLC v. Township of Middletown, 399 N.J. Super. 486 (App. Div. 2008) which held, at page 506, that an entire municipal council who all belong to one political party can meeting in secret, unannounced meetings provided that "only the political implications of [the issue discussed], its 'importance' to the party in terms of votes, the political pulse of the residents of the Township and how to 'spin' items of political importance" were discussed.  In other words, a single-party majority of elected officials can privately meet as long as they are discussing the political ramifications of public issues as opposed to the issues themselves.

Back in 1975, the New Jersey Department of State issued a set of guidelines that explained:
Since a political caucus is only open to one party and would not be open to all the members of the public body, it would not be required to be held in open session. Of course, if all the members of a public body were from one political party, the Law would not allow them to hold closed meetings by simply calling them political caucuses. Nor would the Law allow an effective majority of the members of the public body to use the political caucus mechanism to circumvent the Law's provisions.
Did the Jackson Township Council hold an illegal meeting and then, after the fact, label it as a "typical partisan caucus" to circumvent the Meetings Act?  The public has no way of knowing, as long as the meeting attendees stick to the same narrative.  What is clear is that the "typical partisan caucus" exception is the proverbial loophole that's big enough to drive a truck through.