A few days ago I was in D1 on a TATL flight. Three seats were blocked on the seat map, IIRC 4D, 5D, and something like 3/4/5A on the other aisle. During the flight, 5D was indeed used for pilot rest, with heavy curtains around the seat, but the other seats seemed to be occupied by normal passengers (and one NRSA got a D1 seat at the gate, but I didn't notice the seat assignment).