Oracle Project Control

My Understanding was that in Project Costing if we enter anything at project control at project header level , it automatically gets drilled down to all tasks. BUT in one of the instance when i wanted to restrict specific expenditure to all the tasks even after entering transaction control at the project level it didnt work at the task level so i had to go and assign the same transaction control at Project Task level also.

Can anyone provide any input on this functionality how does project control, rate schedule and other details at project level option drill down to Task or both are independent?