I have worked in some incidents where I could notice that were not clear how the Purchasing Group determination works. Per example, users set the purchasing group attributes in the by role but the attribute is not available in the SRM User Settings.
Role for Purchasing Group:
SRM User Settings
Attribute for Purchasing Group not Available
Sometimes the scenario used is have multiple Purchasing Groups that could be responsible for an Organization Unit and users do not want to enter the default at header on Shopping Cart Default Settings each time coming into SHP or individually on each line.
It is not possible to reach this behavior just using the option by SPRO “Maintain Attribute Access rights by role”
It is recommended to use the Badi BBP_PGRP_FIND. I have created the SAP KBA 1962813 with further information about the standard behavior and the recommended solution.