When an ex employee is rehired, what is the impact on his/her personal details?

Summary:

When a candidate is rehired (with same personal email ID as in earlier records), does this email gets overridden with work email (on the candidate page) after sometime?

This is happening with several rehire cases where the personal email gets replaced by work email.

Content (please ensure you mask any confidential information):

As per raised SR, Oracle says this is seeded behaviour. But when does this get overridden? When the candidate accepts the offer? when he becomes a pending worker? Can someone help with this please.

Also, since the Personal info section of a rehire case (on candidate page) is non editable, how do we stop this from happening- we do not want the work email to get synced on candidate page.