I thought of that too. I don't know, they just seem too flimsy to me. They bend. I don't want the main parts to fail, bending and being straightened until they break. If they are too flimsy, the shear bolt would have to be really weak. Granted, if properly adjusted, the links stand up better. But I mow in a virtual pinball machine here (it's a top quality disc golf course). If and when I break one, then I will make my own. I've already bought the stock to make my new ones.
I think that the ideal shear pin would be small and hard. Soft is not good for this, as it works and wears and fails in time due to normal operation. A hard pin better keeps its shape and fails due to exceeding its shear force. We want its failure to be triggered at a threshold just below that which would damage the link.