I don’t think Hawkeye can be perfect. For one thing, the post is going to move by a matter of inches up at the top of it and Hawkeye can’t allow for that. It can only judge the theoretical position of the post, not where it actually is. And the reality is that is close enough and a lot more accurately then a human can judge it.
The graphic actually showed a fraction of the ball intersecting with the post (at the game I thought it showed it inside the post, but I checked it later on TV, and it didn’t). I agree it should be questioned and not accepted blindly. For example, it must need regular calibration as the cameras and the posts are all out in the open and subject to all sorts of environmental effects, and I wonder does that happen enough. But it is still going to be more accurate then a person and really we just need a final arbitrar we all accept, which it more or less is.