Agreed. Not lies, but a hollow statement by Bethesda.
Possible. It seems to me that random crashes are less common than Oblivion at initial release, but I'll admit I don't have concrete data to back it up, its just an impression. Oblivion at its current patch level is certainly more stable, but thats an apples to oranges comparison since its at a more mature patch level.
Quest glitches, crashes specific to certain UI processes or situational crashes weren't addressed before release, but they generally can't be found with any automated system.
Performance fluctuations can be investigated using automated tools, but it would be a much lengthier process and might not be practical until after all other parts of the engine and setting are set in stone, ie after it has "gone gold".
The biggest performance-killer for PCs are shadows from what I understand. Having the CPU calculating shadows seems like a very poor design decision. Hopefully Bethesda will consider writing code to offload that burden onto the GPU where it belongs.
I wonder if BGS has considered preferentially hiring mildly autistic people to do the testing. I've seen research that suggests they actually make far better QA testers than your average joe. There's even a company in Denmark (called Specialisterne) that hires mostly ASD/asperger's QA engineers and contracts to do QA work.