The structure of the human body is truly remarkable, making it extremely difficult to construct mechs based on human anatomy.
If we have a piece of iron, with a mass of 1, we could use it to build a robot that resembles a human. Many areas would require attention in completing this task, but nonetheless it is doable.
However, this 1-mass piece of iron would not be capable of constructing a human-shaped mech that stands tens of meters tall. Even if we attempted to create it, the mech would collapse with the slightest movement.
The human form is a wonder that eludes comprehension. Every motion it makes involves countless scientific principles. An iron mass of 1 could indeed be used to make a robot the size of an average man. But if trying to construct a ten meter tall mech, this mass of 1 is incapable of supporting the weight it would have to carry.
Hence, the required iron mass to construct a mech of such towering height needs to increase manifolds!