Batul Daato is said when we are defining what is normal. You cannot make your own norm that is different than what is actually normal. This applies to a Shinui in a Melacha on Shabbos, as well as juicing uncommonly juiced fruits. In our case, we are not trying to figure out what something is. We are asking what the person feels.
Here’s one place where feelings play a big role in Halacha.