Neither. I instead call your argument for being fallacious. You’re equivocating on the use of the term “exist.” What God created exists differently from the way sin exists. In a sense, sin doesn’t exis:; it is neither a material nor a spiritual substance but an action, distance from God, a breach in the heavenly relationship. Sin no more “exists” than a missed birthday, nor is any more “created” than a callous word or a blow to the face is “created.”
Because they couldn’t handle the consequences at that time. A stove is a good thing, and yet we don’t let toddlers play in it when it is hot. A car is a good thing, and yet we don’t let our children drive them until they are 15 and 1/2, and then only under close supervision. The ocean is a good thing, but you should never turn your back in it, nor leap in if you don’t know how to swim.