How to cascade visibility on Projects based on Project Organization Classification / Dept Hierarchy

Summary:

We have rolled up "Manage Projects in Organization Hierarchy" to Project Administrator job role in order to achieve the following requirement: I have a hierarchy of department where Dept A is parent, and Dept B Dept C and Dept D are the children. When giving data access set to user, I want to assign only Dept A as security context, expecting visibility will cascade to its children depts B, C, D.

Then we have assigned to Custom Project Administrator Role the data access for Project Organization Classification = Dept A. However, cascaded visibility on children B,C,D is not achieved.