I don't think she has to, though it would be fun if she did mention something about him.
I do think she got inspired on michael a few times. Look at the alterna PV. I think there are some simmilarities to the "Leave me alone" music video. Also ayu sems to have a thing for children in her PVs
Another point is, even though people only mention madonna, unlike madonna, and more likely michael, ayu has a couple of "vocal addictions" that are sort of unique to her and her music alone.