As mentioned there is this whole 'definition' bit that renders the question nearly meaningless, but to reflect my views in the best way possible I went with 50-50/Completely impartial. Sometimes it seems some people seriously don't believe this is a valid viewpoint, which I completely fail to understand. It's enough being tugged at by both sides trying to declare you theist or atheist without getting complaints about that you "can't" think as you do.
Anti-theism is an opinion about belief in God, not your own beliefs, or lack thereof, in God. So it really isn't within the scope of the poll.
It's important to know the difference, but the poll is does not exactly misuse the word. It's true that "Technically agnostic but leaning towards theism/atheism" sounds a lot like they were mutually exclusive, but the closer to the middle you are, the more relevant the "agnostic" part becomes. While all options except for the first and the last one are some form of agnosticism, people who are less inclined to either side might want to emphasize more that they are agnostic. Since I am neither, I refer to myself simply as agnostic and nothing more. I also believe this is why the term is often misused.