No need to disclose anything: plausible deniability is enough. And "bias" can be fixed by ad-hoc quotas.
Or better yet "Why dont employees commit career suicide for relatively minor offences that dont affect them personally and inflict no direct harm?"
They wouldn't out the company because hurting the company for no private gain doesn't help them, and they wouldn't sue the company because they’d be a beneficiary, not an injured party, and so would have no damages to claim.
And also because both acts would destroy their future employability in the field.
Why would they? HR is not your friend.