Earlier quoted context omitted.
It's not PII [1]. That's an actual legal term. Workit apparently wants worker identifying information, and Walmart, like other employers are free to tell their workers not to provide it, but there's no ethical or legal reason they can give to workers not to use it. It's not unlike GlassDoor - lots of companies would prefer you didn't use it, but at the employee level, the advantage/disadvantage ratio is pretty in you…
Your own link lists some of the collected data as PII.
Core PII is: "any information about an individual maintained by an agency, including (1) any information that can be used to distinguish or trace an individual's identity, such as name, social security number, date and place of birth, mother's maiden name, or biometric records"