Makayla is talking to Mia about the whether we ever landed on the Moon. Mia says," I have a theory about that." what is wrong with Mia's use of the term "theory" in this instance?

The word "theory" is usually applied to scientific conclusions that have been based on observations and the results of experiments, and have neither been disproved nor confirmed by these experiments. What Mia possesses is more accurately an opinion or supposition.