MailboxSettings.Read not allowed for user without Admin access.

My developers are working with Office 365 Graph API to pull user's timezones from their Outlook application. They are using  https://graph.microsoft.com/v1.0/me/mailboxSettings/timezone to pull the user's timezone.

For us to be able to pull the user's timezone, the user needs to grant us the MailboxSettings.Read permission.

However, if the user doesn't have Office 365 Admin privileges, they get this "Need admin approval" message:

Does anyone know why Admin approval is needed to pull the timezone of that single user?