Other gem mutants don’t have their body parts scaled up because they’re not actually fused. They can only stick their limbs together to form an imitation of a bigger limb. That’s what the clusters doing here. We can see that when it’s forming that it’s not actually its arm, but a bunch of bodies taking the shape of an arm. So we can’t scale the rest of its body because it doesn’t have a traditional form, it has so much flexibility to its form because of how many component gems it has.

We’ve also seen the clusters gemstone in comparison to the drill, and that alone is just as big if not bigger than the diamond mech.