EHS document attachment storage category BS_ATF_DB hard coded?

I have fully configured SAP EHS incident management using Fiori and am able to create document attachments using the Fiori UI.

The challenge I have is that the storage category I assign to the attachment type schema DEFAULT (which is assigned to my business object EHHSS_INCIDENT and others) in SPRO (Cross-Application Components -> Processes and Tools for Enterprise Applications -> Reusable Objects and Functions for BOPF Environment -> Dependent Object Attachment Folder -> Maintain Attachment Type Schema) is completely ignored and BS_ATF_DB is always used.

I have used category BS_ATF and I have also created my own category in OACT using document area BS_ATF. But when I assign either to attachment schema DEFAULT, my entry is ignored and the system still uses category BS_ATF_DB.

Is this category BS_ATF_DB hard coded or is there any other setting I need to change to use a different category?

Thanks for your help?