The article was very clear that this isn't fingerprinting your devices. You could have zero devices, but you walk into a café and other people's devices are all screaming radio waves, including BFI data, which bonuses off your physical body, forming an image of you

That unencrypted BFI data can then be listened-to by a nearby attacker who would process the data in a ML algorithm, and identify you with near 100% accuracy.

That's what the article said.