I don’t know if this is a US thing. I have no large expectations of HR, but I’m also part of a union and like most places my company has signed a collective union agreement. If there’s a conflict the union will represent you as well. The HR people at my company seem completely OK though, I have dealings with them due to my role.
I’d willingly want to move down to 4-day weeks in some year even with the reduced salary. I’m privileged enough to afford it, and the time regained is absolutely worth the loss in salary and future pension. I’d like alternating Mondays and Fridays, so every 2 weeks you get a 4-day weekend.