I know the monetary amount for the CGS-D and PGS-D is the same. However, the CGS-D is restricted to students pursuing their graduate studies at a Canadian post-secondary institution, while the PGS-D does not have this restriction. Therefore, if your university nominated you for the NSERC scholarship, you will likely be nominated for the CGS-D.
Perhaps the CGS-D provides the decisions slightly before the PGS-D, as they must first inform the university of the decision. This is why some people in their forum have said they heard from their university that they received the CGS-D scholarship, but have not received the official email from NSERC.
Also, I think even if you were to be rejected by NSERC for CGS-D or PGS-D, you will be given an official notification.