Well, I agree that pixelart is mainly approximation, you have to think what exactly to put where because every pixel makes a difference.
Antialiasing is by definition smoothing aliasing on a display which uses pixels. There is LOADS of pixelart which does not have antialiasing. See where I am getting at?
You can not take a picture with a line and fill one side black and say, woohoo look the line is gone. Of course it is, because you changed the application of what was there.
The things you described are all based on the same prinicple, like all living beings have DNA, but they are still different.