Not all GM transmissions go that far without troubles. You got one trans that has an issue but what about the thousands of others that have no problems. Just because a bulletin was issued doesn't mean every trans is bad. It just means they have seen that arise in some transmissions and the update can sometimes help but not every time. There are other things that can cause EXACTLY the same symptoms as you have be advised by others. Could be the car wasn't cared for as well as you were led to believe. After all you are just taking someone else's word for it.