This is the right place to contact System Workbench for STM32 development team
The register definitions are provided by ST, in a standard SVD file, that is embedded in Sytem Workbench for STM32, in directory C:\Ac6\SystemWorkbench\plugins\fr.ac6.mcu.debug_184.108.40.206709081530\resources\cmsis\STMicroelectronics_CMSIS_SVD (if you installed in the default C:\Ac6 location).
I just checked and, indeed, the SVD file locates the SDADCx_JDATAR[JDATACH] field in bits 28..25; I will inform ST of the problem. If this is a problem for you you can correct the file in place waiting for an update.
Thanks for the heads up.