I agree. However, our Minecraft character is a digger that puts fortresses of dwarves to shame, can shoot faster than a brigade of elves, and can survive an in-human amount of blows. X-ray vision seems like something that he might have.
The only problem with that theory is that, our character does not have X-Ray vision. We can't see Spiders, Zombies, Skeletons, or Creepers through blocks. We can't even see the farm animals either. Why should we be able to tell where another person is through the same blocks?