I've seen advertisements where the seller proclaims a normal BP to have "trace patterns" or "trace colors" from the morph parents, even though it was one of the normals from the clutch. Also, advertising snakes as "Spider sibling" or "Mojave sibling" etc. For example, "This normal spider sibling BP shows some nice trace patterns from it's Spider parents" was one I've seen before.

I don't get it. Isn't a spider sibling normal still a plain old normal? Doesn't the snake either get the mutated morph gene or not? Is this so they can try to tack a few extra bucks onto the price?

I can't see anything wrong with putting "morph sibling" if it's true, but if the animal is truly a normal why would anyone care? And as far as "trace" patterns and colors, I don't see how than can be true.