Correct, although it's not that it goes away, more of a it has different properties. The short time I worked in the IOT space, I was a big proponent of explorin

Correct, although it's not that it goes away, more of a it has different properties. The short time I worked in the IOT space, I was a big proponent of exploring an option like this for bootstrapping the WIFI connection in a device that otherwise had just a button or two. The basic problem is, the wifi password needs to be shared with a device without an interface. The traditional method at the time was the device boots with an unsecured wireless network. And an app on the phone is used to connect to the network, and share the wifi password, and then rendezvous on the wifi network to continue provisioning. I think there are some protocols for this that I don't fully remember now. There's lots to consider in this method, such as can someone sniff the transfer, how is that protected, what is the range to pick up, etc. Can someone trick the app into connecting to some other device, etc, etc. If you put mitigations in, how can those be countered. With sound / ultrasound based provisioning (the device I'm talking about already had a microphone and speaker), the range is more limited to who can hear the device. The signal strength is much weaker, an eavesdropper might need to be in the same room. This might allow weaknesses in the overall model of key exchange to be less of a concern, as the properties change to something a lot harder to intercept.