Giant Robots Make Excellent Ninjas...?

Having just recently watched The Iron Giant (and having not fully watched it since probably a decade prior) I enjoyed the animation style and the simplistic designs of the Giant. If I were to compare the animation to another movie, I would use the Disney movie Atlantis which came out several years after, and as far as I remember was the most beautiful art style I'd seen in my life.

However, one massive flaw (or element currently lacking in current media culture) in the movie is that though the Giant is, as would be expected, a massive stompy robot, he is capable of becoming completely invisible to the world. For example, when agent Kent Mansley gets into his car after investigating the destroyed substation, half of his car has been eaten.

But how is that possible? Surely he would have heard (and likely felt the tremors of) the Giant moving over to his car, picking it up, biting out of it, putting it back down, and then walking away. What's more, it does this a second time when it returns to finish the rest of the car

Considering the fact that no person Kent interviews, and even the protagonist Hogarth himself didn't notice the heavy footfalls of the giant, nor the sounds of his consuming various metal objects, we can propose the following theories.

The Giant has a stealth field generator: It seems that when the Giant isn't being looked for, it's impossible to see, so it's very possible that the Giant is capable of cloaking itself, rendering it invisible to the naked eye.

The Giant is capable of levitation, unlike his rocket-propelled flight systems: Its very possible that the Giant has, on the bottom of his feet, repulsers that use a form of anti-magnetic waves that reverse the polarity of the base electromagnetic atmosphere to levitate his body above the ground. Naturally, this would be impossible given his size, as the necessary powersource to lift such a heavy object would be too large for his chassis.However, it's easily plausible that he uses a smaller system to simply lighten his footfalls to the point of inaudibility.

The Giant was subconsciously affected by TV and radio: on atmospheric entry, is possible the giant antenna in the Giant's head picked up the various radio and TV signal waves as he traveled across the atmosphere. In the process, the Giant studied the arts of ninjas, spies, criminals, and professionals, and that information was stored in his databanks, and this knowledge was use subconsciously during his bout with amnesia.

The Giant has a temporal field generator: time around the giant is warped. It would make sense that when active, all those around the Giant experience their time normally, but in reality are actually moving slower, allowing the Giant what might otherwise seem like an unnatural stealthiness and speed.

The question remains though, "Are any of them true?"

Heck if I know.