You mislead. 

The UN has not "backed off"  these reports, they're waiting for confirmation.

From your link:

"We have also been informed that pro-Government forces have been entering civilian homes and killing those individuals found inside, including women and children.

Multiple sources have reports that tens of civilians were shot dead yesterday in al-Ahrar Square in al-Kallaseh neighbourhood, and also in Bustan al-Qasr, by Government forces and their allies, including allegedly the Iraqi al-Nujabaa armed group.

In all, as of yesterday evening, we have received reports of pro-Government forces killing at least 82 civilians (including 11 women and 13 children) in four different neighbourhoods -- Bustan al-Qasr, al-Ferdous, al-Kallaseh, and al-Saleheen. -"