While the math is correct, I think the article somewhat misses the point. What a house outlet can provide, or what a cable can handle has little to do with the unit can provide. Yes the cable will get hot, yes the unit will get hot. But from a pure specification standpoint, the unit can deliver the power. What the article does bring up, although not well, is the basis for the test to begin with. Having done a lot of UL/NTRL testing for medical products, they test for safety only. So as long as under their test conditions the unit is safe, it gets a label. It doesn't mean that under other conditions the unit won't perform better, albiet a bit unsafe.
I agree that its not what people can expect when installed in the home. The test needs to be clarified and changed.
If you think the home market is confusing, the automotive audio market is far worse. Little to no standards at all.