That's part of it. Since it is a driver assist, it should alert the driver since the driver is responsible. After all, how can you have a system that depends on the driver to monitor if the driver falls asleep at the wheel and there is no mechanism to alert the driver? The driver can't monitor if they are asleep. And if there is no mechanism to make sure that the driver is able to monitor and the system is dependent on the driver being able to monitor, that's a weakness. That is why every advanced driver assist system (other than Tesla) uses a driver facing camera to make sure the driver is able to perform their role of monitoring.
The other part of the argument is that the system was on and it did not perform its function correctly. Teslas are equipped with pedestrian detection. So if the system is on and it did not stop for a pedestrian, then the system did not do what it was supposed to do, did it?
But frankly, I feel like there is a double standard here. On one hand, we add more and more advanced systems and claim the car is becoming more autonomous and we give the car credit every time it does something right. But when the car does something wrong, we blame the driver. If we are going to give the car credit when it avoids a pedestrian, shouldn't we also blame the car when it hits a pedestrian?