IIHS works for the insurance industry who will happily throw you under the bus if it makes things more predictable on their side. Not better, not lower claims, more predictable.

The alignment between what is good for you and good for the interests they answer two is not all that much.

But of course, they work very hard to market themselves as peddlers purely of safety, after all only a barbarian would be against safety <mockingly clutches pearls>

This isn't to say that some people they don't care, but giving a crap isn't gonna change the incentives.

How do using autonomous vehicles benefit their claims-settling? Wouldn't it make it unpredictable- in an accident between two self-driving vehicles, who is liable? What if both vehicles are from the same company? Doesn't this lead to extreme variability?

Whould they? If things are too predictable they would be out of job.