You want to create an assembly view where just some components display as shaded, but you don’t want to define the other components as “Reference”.
For doing this, in the assembly file, create or edit a color style, setting the opacity to 0.
Create a new Representation View.
In the assembly browser, make a multiple selection of the components you don’t want to display as shaded in the view.
Then, select the color you have created or modified from the Color drop-down menu for applying it to the selected components.
Finally, create the shaded assembly view selecting the Representation View created in the step above.