Even if many people think that they "aren't very political" and are incorrect, there are some people that aren't very political and this is justified. For example, if you are a 5 year old and you believe you are not very political, you are probably correct. If you have been living in the woods for the last 30 years, don't know anything about modern politics, and believe that you are not very political, it would be weird for us to say "the thought you are not political is itself quite political" rather than "that sounds like a justified true belief."
So assuming it's possible in principle to be "not very political," the real question is how disengaged, uninformed, or lacking in understanding do you have to be for your statement to be true in itself, rather than a "quite political" statement. For myself, I think if someone is disengaged enough that they don't care who will become the next president, and there are no local political issues they will argue with someone about, they are "not very political."
So assuming it's possible in principle to be "not very political," the real question is how disengaged, uninformed, or lacking in understanding do you have to be for your statement to be true in itself, rather than a "quite political" statement. For myself, I think if someone is disengaged enough that they don't care who will become the next president, and there are no local political issues they will argue with someone about, they are "not very political."