I have the same exact experience at my current company. My official performance, which is given by my boss, improved since I started to not care. My output fell, the quality of my work is the same, just less quantity, but for some reason my scores are higher.

On the other hand, I had a job where my performance was rewarded greatly, and I was lucky to be at the right place for that. Almost all of the employees at the same company were not that lucky.