I think that maybe Robert Rodriguez wanted his Super predators to be bigger but because of budget constraints we got what we saw in Predators. The new ultimate predator has the single wrist blade too with red accents on his skin. It could be from another race of predator hunters like super predators in Predators.
There's also a crazy fan theory going on that the ultimate predator is made in a lab with Human and Predator DNA and the human DNA comes from none other than "Dutch" now that's some crazy s@#t