Answer
Full Employees visibility isn't controlled by standard permission-set grants — it's set separately under Human Resources > Organization Administration > Organization Access Setup > Supervisor - Access Setup. Two ways to grant it: tick the 'HR Application Manager' checkbox on the user, which gives simple full visibility of all employees; or explicitly grant the user access to the top level of the organization structure with 'Include Subordinates' checked, which is a more formal HR-authorization-scoped approach. If the goal is simply letting someone view the full employee list (not granting broader HR authorization capability), the HR Application Manager checkbox is the simpler of the two options.