For convenience sake let’s say you have 2 identical lasers, one is blue and one is red. And you shine it on lead (so none of the light leaks through) until the lead doesn’t heat up anymore. Would the temperature change at all between the different color lasers. It doesn’t have to be red or blue, it could be microwave or x ray, just different colors is nessisary.
If you’re measuring energy input by rating on the box yes, but instead of assuming that is your measurement data, they assumed perfect conversion.
It has the same end result descriptively but I’d argue that perfect conversion paints an easier to understand theoretical image, vs a more rigid practical image