Those kind of resistors are made to get very hot. What HKJ was pointing out was that for this application, the resistors being exposed like this, the user has to be careful not to get burnt.
As a coincidence yesterday I bought a second 3 Ohm power resistor to test Lithium drill packs. Here is a picture, it is huge and is rated at 175W. Probably NiChrome wire and it is wrapped around a ceramic cylinder. Same as a heating element. Even dissipating only 125W it gets hot enough to melt the insulation of ordinary house wire should it come in contact.
When I use it to load an 18V (21V fully charged) drill pack I lay it across 2 heat sinks just to keep it off the bench and help spread out the heat. The second resistor I bought is to be hooked up in series to test 40V packs.
Here are 2 - 2.2 ohm power resistors hooked in series. The combo is rated at 110W and got hot enough to melt the insulation of a lead in wire.
So getting back on topic, If you get one of these USB load resistors BE CAREFUL or you WILL get burnt.
Even though I knew, I got burnt. Not pleasant