As per my understanding comma + ing form to be used when it has direct consequence and it always modify the subject of main clause.

Analysts blamed May's sluggish retail sales on unexciting merchandise as well as the weather, which was colder and wetter than usual in some regions, slowing sales of barbecue grills and lawn furniture.

But what does this slowing modify in this sentence.


For members of the seventeenth century Ashanti nation in Africa, animal-hide shields with wooden frames were essential items of military equipment, protecting warriors against enemy arrows and spears.

It correctly modifies the subject

For members of the seventeenth century Ashanti nation in Africa, animal-hide shields with wooden frames were essential items of military equipment, as a protection of warriors against enemy arrows and spears.

In the same question I cannot understand the explaination in OG where it says as a protection of is incorrect because usage of as and a protection has no logical noun referrant. Is a protection is not reffering to animal-hide shields with wooden frames.