I agree, but that does not preclude that God caused that there be evil.
We say that evil is the 'privation of good', which is a careful way of saying what you said, done to mitigate false equivalencies some might draw from saying it in such ways as 'opposition to good'.
But I think it can rightly be said that evil is a principle or a fact, both of which are either directly or indirectly caused by God. I also remind us that evil is given in at least poetic language in scripture an apparent nature at times, crouching at the door, desiring to have us, ruling over us, and related causally to suffering and death.
If darkness can be dealt with in causal language, so can sin. And I think God caused the "what is" —i.e. the arrangement of fact and reality— that we speak of as causing or resulting in moral evil. Thus, we in our stunted thinking (and speaking) can reasonably say that God caused that there be sin.