Details for individual users on the People Page can be populated from different sources, below is a breakdown of where this information comes from and how to confirm.
Creating user profiles on the People Page
Currently, there are 2 ways that users can be created on the people page. The first is manually creating the user from the people page ( the article here walks through that process ). The second way a user can be created on the People Page is through a connected Identity Provider (Google Workspace, Okta, Office365, etc.).
Validating Where User Information is Pulling From
To see how a user was made and to determine where information like Start/End dates, emails, or job titles are pulled from, you can do so by clicking on a user's profile on the people page, then hovering over the 'i' icon on the card that appears on the right-hand side of the page: