In the building trade, yes: “gypsum powder” is the usual name for gypsum plaster in a bag.
In strict terms, gypsum powder is ground gypsum rock, and gypsum plaster is that powder after heating, with small additives that control the setting time. The bags of SIG-MR and PlastoPlus carry the words “Gypsum Powder”, because that is the name that contractors use.