Yes (one of the authors here), the press release came out very badly. The reference to the Clay prize was to try to demonstrate that lots of people care about

Yes (one of the authors here), the press release came out very badly. The reference to the Clay prize was to try to demonstrate that lots of people care about solving NP-complete problems in general... N-Queens has long been known to polynomial time (although there is no known efficient way of counting the total number of solutions). We showed N-Queens completion is NP-hard. This is (in my opinion) interesting to people who care about such things, because it's a long standing problem and has the advantage of being easy to explain. However, it is mainly just a curiosity, and provides a new easy way of demonstrating NP-completeness.