This is asked, not to inform God, but in grace, to bring man to a realization of his fallen condition. The enlightened man is now called to disclose the 'wisdom' gained through his disobedience. I heard the sound of Thee in the garden. His trouble began when God came on the scene. He was quite content with his fig leaf religion, but then God came along and summoned him to give an account.
Fallen man can tolerate sin.
I was afraid. The experience of such fear before God is itself evidence that he has sinned. The only explanation for why he would have fear is because he knows guilt before his Judge. There is no fear in love, but perfect love casts out fear, because fear involves punishment. Before the Fall, God's call to Adam would have been met with the expectation of receiving yet another good gift from the hand of his Creator-Father.