I wonder if there’s a standardized URL to encode SSID and Password or if they just had to make one up.

Presumably Apple doesn’t support this QR method?

QR of course requires a screen and a camera, whereas Bluetooth can work on, for example, an Apple TV type device, or a smart speaker.

EDIT: So then the trick is being able to generate the QR code easily and securely (without having to send your WiFi password to the cloud). Presumably free apps exist to do this.