Well, There's a whole difference between those 2 demos.
For starters... Look at gfields demo's aim. The way he flicks around in that entire demo. You can tell this isn't by the players doing with the mouse. As soon he gets close to a wall the aim turns around and flicks in a millisecond. When he starts to fire at the zombie in the end of the demo, the way his aim spins around the zombie while his whole screen is shaking and even hitting those shots. This is a clear demo of someone using
Aim Assist/Aimbot Cheat.
To QKY's demo... first off he misses some of the shots in that demo. He's a shotgun user and using a shotgun on somewhat of a high sensitivity you need to be able to react and predict where the zombies head is gonna be to hit the shot and hit back the zombie. Theres no evidence of Qky's aim flickering or shaking like in Gfields demo.
Basically, if you see someone like in Gfields demo, shooting while the aim flickers around like that, and the whole screen shaking. Also when the player jumps down near the end of the demo to go for the zombie he was shooting at, while hes shooting his aim tries to turn to a zombie on his right that was killed by KURD in the demo.
To me I dont see the targeting being the same in these 2 demos. Qky's aim shows no point of flickering/shaking or suspicious targeting. While in Gfields demo like I said his entire screen is shaking and flickering around. If you spent some time looking through these 2 demos I think you'll notice the difference sooner or later too. So I would say if you see someone play like in Gfields demo, record it and make a request here on the forum. But remember to get good enough evidence so the cheater can be put away for good