Brake Pads generally don't wear evenly; meaning each pad can wear at s slant. That makes it possible for the part of the Pad you are looking at to look thicker than the other part of the pad and for the Wear Sensor to be making contact on the thinner part of the Pad.
Unless yo find something obvious on the Sensor Wires you may need to pull the Brake Pads to check them.

Concerning Brake Rotor thickness; they can look like they could be resurfaced again but sometimes correcting warpage removes more Metal then you thought would happen.

Also Most Rotors have the minimum spec stamped or cast somewhere on the Rotor. Often on the outer edge of the Rotor if there is room there.

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84 300D, 82 Volvo 244Gl Diesel