I love this question! I’ve seen it asked a few different ways. “What evolutionary benefit did the recoil reaction to the ‘uncanny valley’ provide?”. Thinking about the answer is kinda scary.
I’d think one benefit of being able to quickly discern between the living and the dead would be increased survival chances during death events. If you can see that someone is dead, less likely to face a dangerous predator, natural disaster, or contagion, or at least stop investing precious time in those situations if they found themselves in them.