I think you have to question performances like that whenever the AWP is involved and ask how much of it is just the weapon being really powerful.
Overpass in particular can be such an easy map for AWPing if you have good teammates around you who use flashes correctly to support you. Realistically, Liquid could probably give the AWP to Stewie2k or anyone on that map and see equal or even better performances, if the support setup stays the same.
Nitr0's performances on the old version of Cache were far more legit in my opinion. He used to get so many multi-kills hard entrying onto bombsites, just ripping peoples heads off with a rifle.