Well, ethic is strictly a social construct that allows a society to function as an orderly system within the confines of a mutually accepted set of laws and principles. This is not to be confused with morality. The ethics of a society can be built on either moral or immoral principles. Since this is true, why would God be accountable to a human standard of ethics?
I would agree. The Wiki definition of ethics is, "A branch of philosophy that involves systematizing, defending, and recommending concepts of right and wrong conduct. The term ethics derives from Ancient Greek ἠθικός (ethikos), from ἦθος (ethos),
meaning 'habit, custom'."
I think what God asked Abraham to do was beyond the customs the ancients were normally in the habit of keeping, as it constituted a revelation of total trust in God and willingness to obey Him in the extreme. Abraham likely did not know the sacrifice he was being asked to make would parallel the sacrifice God Himself would make in sending His only-begotten Son to die on a cross, but he certainly understood he was sacrificing what he held most dear to him, making it one of the utmost expressions of obedience to God, and the command "Thou shalt love the Lord your God with your whole heart, your whole mind, your whole soul, and your whole strength."
There's more I could say on this, but I will leave it to see how far you wanted to go with it.
Blessings, and interesting conversational topic.