Just speculating here, but would be useful to find out.

If human drivers see a pedestrian get hit or someone falling down, we instinctively know that's a human there on the pavement (and try to avoid at all costs, just like for pedestrians walking around). Or avoid human-shaped / human-sized objects just in case.

If a self-driving car would lose track of a human as soon as it stops looking like a typical pedestrian, that would be a problem.

>>> The initial impact was severe and launched the pedestrian directly in front of the AV. The AV then braked aggressively to minimize the impact.

Most of us will drive for an entire lifetime and never come across a body in the road.

Aggressively braking to minimize the damage is probably the best you can do, and it seems like that's what the car did.

In this case the newsworthiness comes from the fact that driverless cars are new...