Why dust sensor is throwing different values on change of usb cable?
Can someone please explain to me what am I missing here?


You are missing proper voltage stabilization here. 

If the device end of USB cable shows "hovering voltage" down to 4.6 V, it means that the cable wire impedance plus contact impedance are too high to handle the load. ESP32 might consume significant peak currents (extra 200+ mA) during operation of its radio, which might lead to additional dips in voltage that you might not see on your multimeter, and disrupt the sensor. NOTE: your sensors specifies the supply as 5 V ±0.2 V, so even your DC measurements clearly indicate that your power rail is way out sensor specifications.

You might need to put some serious capacitor at the device side, but you would need to provide a limiter on inrush current (limit the plug-in start-up current to 500 mA) to avoid a crowbar of USB port.