Big John, I understand you confusion. Let me try to explain.
Let's first look at the testing methods. When UL tests something, they will often short the wires together, or otherwise over-load it, and NOT allow it to get too hot.
Yet, when they test a "power limiting" transformer (or power supply), when the output is shorted, they REQUIRE it to get real hot.
Why? How can "hotter" be "safer?"
In a word, IMPEDENCE. With AC, wire flowing through one wire affects other wires near it. This often has the result of restricting the electrical flow through that wire. Of course, this added 'resistance' is reflected as heat. Ever wonder why a transformer that has no load on it still remains warm? Impedence is the answer.
If the wires are fine enough, and the coil is tight enough, then a point will be reached where the current available to even a dead short will be limited. This is what "power limiting" means.
One notable seminar instructor has a dramatic way of demonstrating this principle. While I won't go into it here, trust me when I say impedence does exist, and is what makes transformers work.
Ohms law, V=IR is very true, but as stated is incomplete. It does not account for the continuous changing state of an AC system. To do that with math, you have to get into calculus.
