I would think that a click is something catching and releasing or something not quite tight enough shifting. That said, with a one piece rotor not making a noise and the two piece making one, I have to suspect that the outer disk rotor rivet attachment to the cast aluminum center piece is shifting slightly causing it to click. The fact that a second one from the same dealer is doing that makes me suspect a batch of rotors coming from the manufacturer with the same issue; especially considering that I have never experienced that issue with my Delight Mountain on which I installed the same brake components and have ridden almost 4,000 miles (pads replaced around 3,000 miles). I would think it very difficult to reproduce the same braking conditions in the shop where one could use a mechanics stethoscope to pin point the click,