It wasn’t just the key slot that was the problem.
Internally in the switch assembly itself the detent plunger was changed.
http://www.nytimes.com/interactive/2014/06/05/business/The-Fault-in-the-Cobalt-Ignition-Switch.html
What was worse is that, in the opposite of the Ford master cylinder fire problem where the issue of the leaky pressure switch was compounded by the fact that Ford powered that switch even though the car was turned off, GM *depowered* everything when the key was set to accessory. No airbags, no ABS - which is kind of unusual in the auto industry; usually accessory means that everything but the engine ignition and fuel systems gets power.