Pretty sure dragonscale refers to the look of an "extra set" of scales, though they really do not have an extra set. They have a thicker look to their body, unlike a metallic.
First picture is my dragonscale, second is a METALLIC baby from his spawn. See how instead of the bright sheen of metallic, "Ares" looks as if he were painted a solid color for his body and most of his face. While the fry does not have the solid look, and it does slide into his finnage moreso than the dragonscale.
If you post pictures of your bettas, we can tell you a lot better than just assuming from our imaginations