Master Org is appearing in change organization even if the org access is given only for child org for a responsibility

The Organization Access works as follows:

1) If you assign an organization to one responsibility, you will need to assign it to EVERY responsibility that will have access to it.
2) Any organization that is NOT assigned to at least one responsibility is available to ALL RESPONSIBILITIES.

So, if the Master organization is NOT assigned to ANY responsibility , it will be available to ALL RESPONSIBILITIES.