See https://github.com/larsbutler/oq-engine/blob/238f3d09b359181d2264d1afc44460d352bd5e11/openquake/engine/export/hazard.py#L243. There is special handling required for GMFScenario, because it was not build to be consistent with the other outputs. :(

I see that I need to remove this case here: https://github.com/larsbutler/oq-engine/blob/238f3d09b359181d2264d1afc44460d352bd5e11/openquake/engine/export/hazard.py#L139