If you claim otherwise, you are claiming the Fall happened before that incident, or that God created imperfect beings while claiming it was all good.
It isn't what Adam knew or didn't know. It's what Eve knew or thought she knew.
Christians shouldn't be naive that we can't be deceived. We're warned over and over in scripture to beware to it. And if I asked every Christian here if they had a choice whether or not they want to be deceived, what do you think the results would be?
While Eve was deceived, Adam was not.
...you are claiming the Fall happened before that incident, or that God created imperfect beings while claiming it was all good.
No, the fall did not happened before the "tree" incident. Nor did God create imperfect beings. Perhaps God wanted to show Adam what choice he would make if put into that situation. God knows a lot more about us then we know about ourselves.