If you were offered Zurich, that's not the factory authorized extended contract anyway. The factory plan is from AMT, and is branded Chevrolet, Buick, Cadillac, or GMC Platinum Protection. Zurich is an insurance company offering an extended plan, but since they have no vested interest in the vehicle (same as other third-party providers), they have no incentive to cover a borderline repair - they won't make money that way.
For the authorized GMC plan, see here: https://www.gmc.com/protection-plans