Headline is hyperbole. According to the linked page, iOS devices leak some network information and it may be possible to analyse this to establish where the device's owner lives.
How is this a hyperbole? The device broadcasts MAC address of previously connected, which is easily converted into geographical coordinates.
as far as I remember this is a feature, the wifi connection stack on osx is trying to connect to recent wifis first with the mac address because that is much faster than trying to get a new lease and so on
It also causes occasional IP-address conflicts. Had this happening before and traced it to an iPhone using an IP-address it did not have a DHCP lease for.