Q:

Account Team configuration- What Opportunity or Case Access Private means?

At the time of defining Account Team, I can see Opportunity and Case Access can be defined as Private, Read Only, Read Write.

If user has access to the Account then user could automatically have access to Opportunity, Contact and Case records and vice versa because of Implicit Grants.

I can understand Read Only and Read Write Access. How actually Private works?
Is that anywhere related to this role definition and access rights:
Is that Private is only applicable for "Users in this role cannot access opportunities that they do not own that are associated with accounts that they do own"?
If that depends on above statement then how following statement is valid about Implicit Grants?

Grants that occur when non-configurable record-sharing behaviors built into Salesforce Sales, Service, and Portal applications grant access to certain parent and child records. For example, with this default logic, sometimes referred to as built-in sharing, users can view a parent account record if they have access to its child opportunity, case, or contact record. If those users have access to a parent account record, they can also access its child opportunity, case, and contact records. (Refer Record-Level Access: Under the
  Hood)

Appreciate someone's guidance.

A:

The Private option on Account Team Members simply means that the user who is a team member doesn't get any additional access to the cases or opportunities on the account, as specified. This is similar to how the role hierarchy setting works, except that the role hierarchy option is for the owner, while the team member settings are for additional users that are not the owner. Private works for any role hierarchy sharing setting, because they affect different users.

