No, partitions cannot be specified via the nvsetcreate command. It can only be done via the GUI. The reason is that nvsetcreate is a generic NVBU core command (like all other NVBU CLI commands) and it can't create a selection set that is specific to any particular plug-in. NVBU core only has knowledge of the selection tree nodes that are displayed. The partition info is handled and interpreted by the plug-in code.
The answer is 'No'.