Sometimes I wonder at American English. If one letter will do: use it, whether it makes sense or not.
Let us take a look at a simple thing the sound of a horse makes, a whinney, it communicates to us; a whiney is something different, but it is used and disturbs a story. The same with a small pasture, or a penned in area to retain animals: a CORRAL. A simple Spanish addition to Western vocabulary.
Now let us consider a polyp using calcium and natural adhesives to make for example the Great Barrier Reef. It is made of CORAL, not a hospitable place for horses.
But Ron seems to feel a similarity of words is sufficient to deliver meaning to his Readers so they can enjoy fully his tale of the West, which if it wasn't for those errors would be well worth the attention of us all. I suppose it is a sign of the times, necessary to squeeze as much information into a tiny screen to allow people to read it going 60 mph in rush hour...