The Shulchan Aruch rules that beis din can physically coerce a person to marry against his will. So Rabbi Schachter isn’t making a chiddush here.
Rabbi Schachter’s speech making this statement that a Posek can order two people to marry each other is available to hear directly from him as the shiur he said it at is available as a recording on yutorah’s site.
During the same shiur, Rabbi Schachter said whom to marry, whom to vote for and what line of parnassa a person should choose are all halachic shailos within the purview of Daas Torah that a Posek is deputized to issue binding halachic rulings for a person to follow.