Han still managed to evacuate all the population and soldiers, so they're still in the same situation as before. The objective is the complete conquest of Han, and not merely of a piece of territory, so I'm not sure what the change in the situation is? I guess they'll explain more in the coming chapters, but so far it seems to me that Qin's difficulties of conquering Han without losing too many soldiers remain pretty much the same.
This reminds me of Zhuge Liang's conquest of Wei's 2 commanderies, which turned out to be a minor victory because Wei managed to depopulate most of the territory beforehand.