"The belt touches a part called the "Hall Sensor", which sends the speed of the belt that's touching it, to the circuit board."
The technical term is 'hall effect sensor.' It's basically a speed sensor, yes, but the whole point of it is that it doesn't touch anything. Sort of solid state, so it won't wear out. It requires metal to pass by it (and the absence of metal), so likely there are metal bars inside the brush roll for this purpose. I'd be very surprised if the belt itself had metal in it.