I don’t think it is a coincidence but I am keen to understand how such user tracking works.
You can check out companies like Geocommerce, they do location based targeting, but also follow the user from device to device.
There are other methods as well, just giving you one data point. My knowledge comes from having done it, and yes I glossed over a lot of the details.
TCP Headers SSL Cookies language headers fonts
Different browsers will render the same page in different ways which results in resources being loaded differently, you can detect this. They will also send different headers for different types of content, for example a picture could be byte served html generally isn't.
You can easily detect if its a mobile device and then ignore ip but instead track an ip range.
There are lots more ways to track a device online without cookies or IP, its fairly easy. The devices are often connected by sharing a login or an ip if both are on your wifi. Once the connection is made between devices its never forgotten.