I think maybe the whole concept of "this is a known issue" is what has you mislead. I don't think that when this phrase is used that it means that it was a problem when it rolled off the line. Rather, I think it means that it is a common wear item, or weak point after modding.
All cars have things that go bad, I had a 1989 Buick Reatta that was as predictable as the sunrise, if I listed in order the things that went wrong with it then I bet 90% of the Reattas out there followed in the same order and age. Point being, saying "it is a known issue" basically means that you should expect it to fail after a certain amount of time, as with any vehicle. It doesn't mean it was a crappy car, it just got old and wore out in a highly predictable fashion.
Also keep in mind that a lot of the posters here have heavily modded their GPs. An unmodded GP will likely never have any major failures in the drivetrain. But then if you are pushing 300+ HP on a pre-03 tranny then it is a "known issue" that the 4th shaft is weak. Not that it would ever fail in stock configuration but any builder needs to address weak points when modding.
Just an added point, in my mechanical engineering program in college, the manufacturing advisors who worked with Toyota told us that it is common industry practice to engineer a car to last 7 years. Anything more than 7 years should be considered a bonus. They made no mention of design milage. Basically what this means is that blower motor brushes, for example, are designed to last through 7 years of average use. Plastic trim clips and dash panels will get brittle and crack after 7 years of UV exposure and heat cycles. This is common practice for most vehicles sold in the US, not just GM. Just something to consider.