In my opinion, I think they should be separate because the two variants are different, technically speaking. The /0 and /5 will have different liveries and the model of the train is different as well. I would sy this makes a difference to other trains with different variants as the variants are basically the same other than the amount of cars.
Sorry about my short edit war on the Millcastle Racecourse article. I am currently banned from the SCR Discord and am unable to view the sneak peeks, making my only method of viewing sneak peeks Twitter. Can you please provide an image of the sneak peek.