Yes that does not look very appealing, it is very time consuming (i.e. labor ) for clean cuts on a radius thats not pre ordered, since you have an exposed raised bond beam with stone this was an attempt to match the precuts, this needs fixed I would have to go way in depth detail, but i can help.

How would you fix it?

And how would you have done it originally to make the edge look natural?

If they are going to split it that way they need to finish the chisel job, and chisel the entire edge. That is how it is supposed to look.
Generally it is just scored, and hit with chisels till it splits.
This gives a nice split face look.
Not making deep gouges like this. Not skilled masons.
Cutting it clean is the easiest, but in my opinion looks terrible.

I found out what they did was use a saw to cut the stone, and because they knew I didnt want a smooth edge, they hand "chipped" up and down on the edge to try to make it look "natural". I still don't want a smooth edge. Not sure what to do now other than make them start all over.