Have you read the article? They're claiming (!) that they would use ads on websites to use mic data. If you know anything about Android or IOS, you'll know that you have to give mic permission to your browser for it to have access to anything. THEN the browser itself checks if a website needs access to your mic and you have to willingly give it. And lastly: Android indicates when your mic is hot with a green dot. So all of their claims are bs.
Come back if one of the OS developers admit to always listen on an OS level.
Several days? Was this a siege? In any other case they'd torn down the house.