HR is payed by employer, HR does not want to get fired so they will always protect their job and employer. Never ever discuss with them anything unless it is onboarding or offboarding. Refuse exit interview it can only hurt you. Anything you say on the exit interview will be added to your file and it could lead to not rehirable pile or bad reference pile.
If you end up with HR write some meeting notes and after meeting write them an email summarizing things what you agreed on (so you make some paper trail for suing if they don't hold their word) It could win your case if you end up suing the company.
Bumping this up for visibility, it's good advice.
Source: @rfd+1qY9q3le