It's basically up to the hardware manufacturer. Sony upgraded the PS4 to the PS4 Pro and counted it as the same sales. Microsoft upgraded the Xbox One to the Xbox Series S and counted it as different sales.Apparently you can just upgrade your console and keep adding to the same sales total. Like if ps5 had been called the PS4 super-pro they could aim for 200 million ps4s sold! Then we could just add graphics sliders and resolution choices to PS4 games and stop all this scalping nonsense.
Makes me wonder why we count things like this. Isn't it userbase and software sales that are important over hardware anyways