AX 2012 R2 CU7 - Project - WBS - where is used default category assigned to tasks ?

HI Everybody,

does somebody notice where is used default hour's category assigned to task on main WBS screen in Project module ?

I found the following explanation from MS:

By default, the category is automatically copied from the default category for hours in the Project management and accounting parameters form. You can modify the category for a task.

Is it used only as default when hour's cost estimation is created for given task ? or somwhere else ?

Thanks for any idea...

Witold Adamiak