I hoped for some analysts of how it's implemented (there's probably a lot of clever low power-pings and cryptography involved), but the linked Twitter thread is purely "WTF? Get off my lawn!"
If you read down the thread a bit (I’m the author) you’ll see that it’s (probably) implemented by caching cryptographic beacons on the UWB chipset. It’s not documented by Apple, however, which is the reason my thread is a little critical. I think it should be.
