I'm optimisticly guessing the devices talk to the router in such a way that their mac addresses can't be eavesdropped out of the ether, and there's enough mac addresses in the universe that cycling through spoofed addresses is unlikely to be fruitful.
Though, I could learn a device's mac address by setting up a competing wifi device, possibly by a: having a battery-operated one during a power outage or b: being friendly with my neighbors "sure you can borrow my Wi-Fi".
Now I'm curious how mac addresses are determined (like, is a Pixel 3's mac address going to follow a specific pattern?) and I'm going to go look that up.
It also twinged my implausibilty meter when they said there were several easy to find podcasts and blog posts on the depths of AiW, but didn't link to any....
Edit: the first, long comment made me think it was some autist's [not derogatory] special interest and that they were too deep to explain it well. The second comment made me think that was not the case.