That is really shocking. At the same time, I'm not surprised. What a horrible, horrible company. I'm glad you're out of there now, but it's disappointing that you had to waste your energy on all that bullshit that followed.

In one of my previous companies, it was the line manager who ticked the "good to rehire?" box. They'd have the best perspective, but I'm sure HR could have overridden that if they wished. That company didn't give exit interviews; there was just a form to fill out (which possibly disappeared into a black hole). Their trustworthiness seemed borderline, but I erred on the side of caution.