You’re wrong, btw, the Google Prompts feature is Default and cannot be turned off.
Only if there's a previously-authenticated device. That setting can't be enabled without a key, and one of the required keys is produced locally by a logged-in device (which is why your device is trusted to stay logged in indefinitely). If enabled without a key, it's nonfunctional and should error itself out and revert to a disabled state.
If that somehow hasn't happened (which, in all honesty, would be very surprising to learn) and the setting is enabled on your account, then that'd be something you'd need to submit a request to Google to have fixed, otherwise you have zero recovery on that account.
Are you a thousand percent sure you've never had any other device logged into that Google account? When you attempt to log in, it should show you the device name it's sending the request to. For instance, when I log into my Gmail from an Incognito window right now, it says to check my Pixel 6 Pro. What's it saying for you?