I love the idea of a million google drones sitting there listening through people's mics to see if they can catch someone talking about backlinking or scraping content though. They've probably got copious notes on the present you bought for your Aunt's 60th birthday and are trying to work out if it's code for pbn posts.
I'm fairly sure I've seen almost exactly the same article written about mac speech recognition about ten years ago and for every iteration of browser/os since. Ultimately, it's the internet and as we've seen, virtually every browser has a hole in it. If you think yours doesn't, it just hasn't been exploited yet.
You can go all Ron Swanson about it and go off-grid or just take reasonable precautions and disable your hardware if you're really worried about it. Personally, after taking the blue pill, I'm happy to welcome google as our new overlords and masters of everything...