Big Toe
You are getting mixed up with the "gross" and "net" power ratings terminology which is one of the reasons I why hate that it is stated that way. When people think of gross, they think that the engine is only being tested. While this used to be the case pre-emissions, this is not the case post emissions.
Instead of thinking of J1995 as "gross" power ratings. Think of it as an "as shipped" engine power rating which includes all devices that make it emissions legal. For example, if you go into Cummins Quickserve and input my 2014 2500s engine serial number, it will show all components that came with an "as shipped" engine to Ram.
You will notice below that the aftertreatment device is apart of the "as shipped" engine.

Then if you breakdown the aftertreatment device you will see what catalyst come with the engine.

I believe Cummins gets these aftertreatment devices from another supplier for the pickups, but I know they make them themselves for the larger engines, fire pumps, and gen sets.
So think of J1995 as an "as shipped" engine power rating rather than a "gross" power rating.