When R30812 is ran with 07 cost for purchased item, issue of these item in WO is valued with 07 even

Hi,
I'm having trouble with Manufacturing accounitng.
It seems when R30812 is run with 07 for cost method for purchased items, issues made from WO are also valued with the method 07 even though we have 02 for costing method in the branch item for these purchased items. What to to have the issue for the WO valued with the 02 costing method.

Thanks. 

Here is a case :

create a manufactured item (code : MAN)
create branch plant item for MAN
with inventory / sales costing method = 07

create a purchased item (code : MAT)
create branch plant item for MAT
with inventory / sales costing method = 02

Enter a cost of 40 in the costing method 07 (for item MAT).