The attestation will include a unique ID of the phone, so that if you get banned you have to keep buying new phones and keep paying money to Google. Google won't stop this because it makes them money.
And the official Google OS just won't feature remote-control software.
There's also remote control hardware (a printer-like device can operate a touchscreen). But the first point stands, yes. Be it a phone or another hardware attestation device, they and Apple will be giving "I am human, let me participate in society" checkmarks out, directly or indirectly for money
Or keep stealing IMEI IDs. Now regular people will start getting banned from the internet because of bot activity. You would open your phone one day and see "You have been disconnected from society" and there will be nothing you can do.
I know that's the final destination, but I didn't see that listed in the requirements page linked above. Any proof of this affecting the current implementation?
Bluetooth is generally used to prove that the two devices are co-located, which makes it more complex to do your proposed kind of deployment at-scale. Bespoke solutions could perhaps work around for some smaller number of devices, this QR code layer by itself isn't intended to stop 100% of workarounds.
These passkey QR codes don't need to use Web Bluetooth API, because they utilize the WebAuthn API. The website itself isn't given access to the bluetooth, the task is handed off to the browser, which as a native application, can access bluetooth and abstracts the bluetooth away.