“You can tell us anything. That’s what we’re here for.”
No.
HR is here for the company. The company pays their salary. The company writes their performance review. The company decides their bonus. When your interests and the company’s interests align, HR is your friend. When they don’t, HR is the company’s friend, and you are the subject of a meeting you weren’t invited to.
This isn’t cynicism. It’s structure. HR can’t serve two masters. They chose the one that signs their checks. You would too.
The person who tells HR everything should understand: everything you say is a memo in someone else’s file.