Prototype or mock up?
Probably a bit of both. Sometimes, when companies want to show at a fair or make a presentation, and don't have a product on hand, they fake one up as a 'mockup'. That appears to be the case here with poor Shadow. Is this supposed to be Super Shadow? (You might think: oh obviously!--but remember, TI is a fan of whacky paint & made Space Fighters & Metal Force which had nothing to do with anything)
Also notice that his shoes, socks, & gloves are also pearlized/metallic while his super form only the skin/fur/eyes changed. Is this a painted regular Mega Bot Shadow? Absolutely. They painted over his red with a different red & threw gold on over the black. (note chipping at joints)

This would be suspect of a fan hoax, but the feet/shoe/gloves really are different. Also look how BAD the eyes are. The pupils are off to the bottom/edge, he looks just awful. They didn't even use the better face that they clearly had sculpted for this "extra edition" they were planning on making.