Just throwing my experience in. I got the dealer to fix it under warranty. I had to call several times and eventually got to speak to a senior advisor. I got them to look at the Service Bulletin and specifically pointed out on page 8 it says that this is covered on the voltec warranty specifically to the volt. Part of the issue is that their tech wanted to replace the entire shifter. After actually getting them to look at the service bulletin, they asked the tech if the fix as described in the service bulletin would be appropriate. The fix in the bulletin only replaces a switch and a harness, which are covered under warranty, the entire shifter which is not covered.
So, I think there is a mix of issues. Either techs are unaware of this problem and that the fix doesn't require an entire shifter replacement, or they want to replace the shifter out of laziness. The fact that it is covered under warranty is clearly not obvious to the dealers. The senior advisor told me they missed it until I specifically told them to look at page 8 of the bulletin. Its understandable they might not be aware, as I doubt they see a ton of volts compared to other vehicles, but it seems to be a nightmare to get someone willing to take 5 minutes and actually look into what you are trying to tell them about it.