I’m wondering why you would need sledge hammer fists if you weren’t going to use them in fighting. There aren’t too many activities out there requiring sledge hammer fists other then hitting the top of the radio to improve reception. As a gardener, I could use some shovel arms or some pruning shear hands.
The weights are intended to be worn while training, to increase your own strength. Not to be worn during a match, where they’ll give you the capacity to hit much harder — something which you do NOT want during a martial arts bout. Speed rather than power during a competition. If you’re actually beating the crap out of someone, feel free to wear them.
I don’t think the weights are meant to be worn only during training. The text in the second paragraph clearly indicates that you’re supposed to wear the weights pretty much all the time, thereby forcing your arms to build the extra strength needed to handle the extra weight. As you grow stronger you could add even more weight, until you become strong enough that your muscles can tear themselves from your bones.