Does a pedestrian have to wait for another green signal at a staggered crossing in Northern Ireland?

Yes. Staggered pedestrian crossings with an offset central refuge operate as two separate crossings.

Rule 28 says to stop on the refuge, press the button again and wait for the green pedestrian figure for the second section. A green signal for the first road does not give permission to walk across the next carriageway. Check that vehicles have stopped before stepping out.