This far out, UA has no reason to sell the J / C seats in any discount bucket. People booking this far out tend to be inflexible and price insensitive. I would never book a domestic flight more than 90 days out other than for a major holiday, e.g. the day before Thanksgiving, or special event such as the Super Bowl.

Ignore the seat map. All it shows is that a seat has been selected not sold. Moreover, UA is predicting that it will sell those seats at a higher price and, if it does not, it will then drop the fare.

Don't forget that you also have other choices on this route, all including premium service, e.g. AA to JFK (with both F & J) and DL to JFK (J only). Finally, B6 offers MINT -- a J product -- on that route as well.