>>38842033I'll keep breaking it down for you.
Onix's model moves in a much different way. If they had animated Steelix in the same way, there would be no issues here.
But they have chosen to animate Steelix sprawled out long-ways. If they had this animation traveling over the ground, it would clip through any surface that is not completely flat. To avoid this, they raised his model a couple feet above the ground. Do you understand?