I was wrong, my Pro's blindspot warning works exactly as VW intended. It's all in the Owner's Manual U.S. edition under "Lane Change System (side Assist)" on page 156.
If I understand the explanation, it works like this: a car passing the ID.4 will cause the blindspot warning to light up. However, when the ID.4 passes another vehicle, the blindspot warning will only light up when the difference in speed between the two vehicles is less than 10 miles per hour. If the difference in speed is more than 9 MPH then blindspot warning won't light up. I just verified all this when I was driving on the freeway - yup the VW system works as intended. I think I see the reason why VW did this, but maybe they are just splitting hairs. If the blindspot light came on whenever the ID.4 passes another car then I think that too would be acceptable, or maybe better (unless if there is some technical reason).
So far nothing wrong with my Pro (2,423 miles on the clock) I'm delighted to say.
It was giving me strange messages at one point to the effect that my car had 10,385 miles on it, "Inspection service overdue". I even have photos of that mileage which appeared on the "Status" screen.
How could something like that even happen? Can these cars be hacked?