The wikipedia article could in no way be summarized as "we let Korea print $100 bills". A first sentence is "A superdollar (also known as a superbill or supernote) is a very high quality counterfeit United States one hundred-dollar bill,[1] alleged by the U.S. Government to have been made by unknown organizations or governments". The body of article follows this. Only dubious allegation that North Korea (among several groups) print them and no allegations that the US allowed this.
It happened/may still be happening for all we know.