Exported XER file contains all RISK TYPE data on EPPM database, only assigned RISK TYPE in PPM database, why?

Does anyone know why XER contains all RISK TYPE (Risk Category) data if connected to EPPM database, but only assigned RISK TYPE exported from PPM database?

1. Connect to PPM database.
2. Export a project in XER format.
3. Open this XER file in notepad and search for RISK TYPE.
4. No RISK TYPE data contain in XER.
5. Connect to EPPM database.
6. Export a project in XER format.
7. Open this XER file in notepad and search for RISK TYPE.
8. Whole RISK TYPE data defined in database is exported in XER. (regardless assigned to a project)

Problem is with unused RISK TYPE data contains in XER, the XER file become large.

Expected behavior is only assigned risk category in XER is expected behavior.

does anyone know the reason why P6 behave this way?