You can now restrict profile field categories to prevent users from seeing fields they don't need.
By choosing group restrictions, all profile fields within this category are only viewable and editable for users within the configured groups. Users from other groups will not see these field in their profile. By default no groups are configured, so every user has the profile fields from this category.
This is not a security restriction, it is meant to reduce overhead for users! If a user has set a field, which is restricted later, the value can still be found in the search.
Theo Schröder is in the "confluence-administrators" group, so he can see and edit all fields inside the "Admin only knowledge" category.
Kathrin Holmes is not in this group, therefore she cannot see this field in her profile.