My Pocophone F1 has a button to generate a QR code from a network in the settings app, I guess they added a special permission for it.

Whatever is currently on the OnePlus 6 does it.

At last my Pixel 3a have that option. On the network settings you can click "share" and it will give you a qr code as well as show the password in cleartext in the screen. It does require you to enter your password or scan your digital to go there.

You're right but the UI that they're referring to is in a system app

I've seen it since 9, I don't recall seeing it in 8, but it's also hard to tell where I've seen it due to manufacturer customisation.

I think it came in roughly 9 though.

On my Samsung 9+ with Android 10 it is under WiFi, settings, button on the bottom of the screen.