I have an S20 Ultra and I haven't checked the literal current. My phone says "charging", "cable charging", "fast charging", "super fast charging", and "super fast charging 2.0" depending on how it negotiates with the charger. Plugged into the USB ports on the car, I get "charging," and it barely provides enough power to run
Android Auto and not lose battery. When I plug the same cable into a decent 12V charger plug, I get "super fast charging." I suppose it's possible the cable is terrible and limits to a low amperage, and the difference is that the 12V charger uses a higher voltage, but I doubt it.
When you get 1.2-1.5A, does your phone charge quickly? Like within an hour?