Why Did The Prisoners Have To Wash The Floors Of The Blocks Before The Evacuation?

At the end of chapter 5 of “Night”, Elie Wieselrecalls that the head of his block ordered that the barracks be cleaned before they leave to go on their Death March to Buchenwald by way of Gleiwitz. Although Elie himself does not give clear explanation as to why this order was given, he says to himself, “Suddenly the Blockalteste remembered that we had forgotten to clean the block. He commanded four prisoners to mop the floor... One hour before leaving camp! Why? For whom? ‘For the liberating army,’ he told us. ‘Let them know that here lived men and not pigs.’ So we were men after all? The block was cleaned from top to bottom”.
The night before the liberators were due to arrive the Blockalteste ordered men to clean the blocks. They wanted to make it look like thousands of men weren’t being treated poorly. To me, this is very ironic. The Germans were killing and torturing these people but once they realize people are coming to help the prisoners, they wanted to make a good impression. The Blockalteste wanted to make it look like there weren’t feces, dead bodies and other things in the bunks where people slept.
With this, Elie stands there thinking "Were they men after all?" Especially after all that they had put the Jews through. They put them in labor work,treated them like slaves, and slaughtered them like animals. He recalls all the things that has happened. Yet how they could pretend to have been treated like humans when they weren’t treated so.