FR's skin page says this:
"Scars, light wounds, and blood splatter are generally okay."

That's a minor scratch, and I can easily see someone thinking that it would fall under 'light wounds'. It certainly fits that better than "We do not allow skin designs that depict creatures that appear to be suffering from massive wounds and/or designs that contain excessive gore"

The arrow one was told it would be fine if they removed the (pink) blood around the arrow. So... the arrow being embedded in the dragon was fine, but a small amount of blood wasn't.