Don’t know about the bug you linked (will read up on it later), but I can easily provide radio captures to prove that most Android devices do what I described,

Don’t know about the bug you linked (will read up on it later), but I can easily provide radio captures to prove that most Android devices do what I described, with no “hidden” networks ever in use. There are retail analytics startups who literally use this exact type of data to allow brick and mortar stores to gain insights into their passive customer behavior. Source: I used to work for one of them and designed and built a bunch of the hardware / software stack.