The rear window electric grid lines vary in thickness as they run from side to side. Design intent is to evenly distribute electrical current over the entire glass surface.
This does not affect or reduce the performance of the rear window defogger.
When repairing a broken grid, the repair should be the same thickness as the grid line at the point of repair.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.