In the US, it’s always considered the fault of the person who read ends someone.
This is simply false. Brake checking is explicitly a traffic offense in some states, and can get you cited under something like reckless driving in some other states. Your insurance company is not obligated to find the other driver at fault if you're cited for brake checking.
Your reply is totally relevant in the context of someone blaming driverless cars for stopping when it doesn’t know what to do.
Second, I'd expect Cruze to at least have civil liability if their cars glitch and brake spontaneously, resulting in an accident. Since spontaneous braking is something autonomous vehicles have struggled with (Tesla at least), yes, it's relevant.
They literally have signs on them that say "warning, stops suddenly" , not a joke, literally
But braking for safety is always allowed and the person behind you is supposed to leave room to allow that.