I think I have to agree. I understand the impulse to say that it's implicit, and certainly the desire to build a quality product usually is. But in reality, to actually verify quality before you ship often requires a lot of costly infrastructure and time-consuming work. So in practice, it really is a lever that often gets sacrificed---usually at the alter of the timeline. You could argue that a feature that is broken isn't a feature, but there are many subtle degrees of broken-ness. A bug that happens 1 in 1000 times might be acceptable, or it might not.