Graphical Organization Structure - Help on understanding how it works?

For the organisation structure below. Say we have 4 graphical positions as well.

Level 1

Level 2

Level 3

Level 4 all with position access generated. E.g.

Level 1 has access to Lvl 2, 3 & 4

Level 2 has access to Lvl 3 & 4

Level 3 has access to Lvl 4

When we go to supervisor access, Employee A (Position - Level 1) -  (Org - CEO 1) cannot see FI01 or anyone below.

Employee B (Position - Level 2)  - (Org - FI01) cannot see FI02 or anyone below

Employee C (Position - Level 3) - (Org - FI02) cannot see FI03???

In Supervisor access setup we then turn on include subordinates. Employee B (Position - Level 2)  - (Org - FI01) can then see the employees in FI02 & FI03 but also see other staff that are Level 3 and 4 across the rest of the organisation in Ops and Sales etc. 

Why does the organisation tree not just allow you to see staff below that part of the tree as long as there position allows access to it? 

Yes you can individually go through and allow access to elements in the organisation structure manually but this seem overly convoluted. We are implementing IFS to approve efficiency not create a new task for an employee to keep updating access when people leave and join an organisation.

Thanks in advance for your help.