That is true in general. But in this case, what new information arose in the intervening months? There were no reported cases. Presumably the only thing that changed was that Nest's QA team eventually got around to doing what they were likely too busy to do before release. So this appears to be a classic case of trade-off between safety and time to market. I don't presume to correctly judge what would be the right values to plug into that equation, but I think it is fair to raise the question.