EDIT - found the answer:
> Because the metallic conductor is essentially a mirror at the wavelength of the laser, the process is effectively “self terminating”, that is the laser vaporises all of the insulating material down to the conductor and then stops, so no process control is required to prevent damage to the conductor.
I'm imagining some researcher after years of investment and experimentation eventually accidentally discovering the solution: "you mean it just shuts _itself_ off?!?!".
If you want to laser through metals, you need a different type of laser. Just as getting through concrete needs a different tool (say, a hammer chisel).
A knife blade and a masonry chisel are roughly the same type of carbon steel tempered to a similar hardness.
They will both scratch and damage concrete.
But would you like to chop through my sidewalk to get to the water main with a santoku?