It still works because those CGNAT shared IPs still vaguely correspond to a certain geography. It won't be accurate enough to target a specific home, but still accurate enough to target a specific neighborhood, for instance.
Assuming an ext-IP (60k ports) can easily represent 100 household if we statically assign ports. Given CGNAT with dynamic port allocation this can easily go up to 5x? That's wildly inaccurate given the core problem is to "target" a small set of users which is based on this geo info. Not sure how well this elephant sits in a room full of engineers solving this specific targeting problem.