Hi Hayashi,
yes that is the case. If you want to enhance the SUS screens with additional fields that is only possible by modifying the BSP views, except for the standard tables. They can be enhanced with additional columns in the SUS customizing in SPRO.
If you want to modify BSP views, I suggest to copy the standard view to a Z version and specify this custom view in the SUS action customizing in SPRO. If a note is released for a standard BSP view, you will not get any conflicts implementing it. This means of course you will need to take care of implementing the changed view code to your custom views manually each time.
regards
Zoltan