Typically, only when Duke basketball underclassmen are passing on becoming surefire draft picks do they announce their returns for the next season. Neither Wendell Moore nor fellow freshman forward Matthew Hurt fit that criteria. So it's highly possible that neither one "officially" says anything to the public and just simply comes back (though Moore did hint at such back in March).
And now they seem to have even less reason to make any fuss about their decisions. Per 247Sports Duke writer Adam Rowe, freshman guard Cassius Stanley, who declared for the 2020 NBA Draft on Tuesday, told reporters via a Zoom call on Friday that Moore and Hurt will indeed be sophomores in Durham.