Just like many physical and non-physical (software) products, very often, literally nobody reviews/verifies/checks them.
Google will learn from this mistake, and next time they'll use a fancy MEMS microphone or a similar technology and place it inside a semiconductor package.
When do you think such a feat will be discovered by independent researchers? Probably never.
There's also the reality that they can simply change the components/layout without ever telling anybody about it.
People just keep buying the same boxes without even being aware that the hardware inside these boxes might be completely different revisions.
Who's to say that future batches of Nest won't have cameras added for "future use"? Who's gonna go through the effort of checking every fresh batch of Nests for revisions like that? And what are the chances of actually catching it when it's only rolled out in small batches?
