I have said before, that I do not just rely on tests. It is just a starting point. I do in fact, read a lot. I just don't care to grab a book on it. Plenty of stuff online that is easier to digest. I am well aware of my "learned" behaviors, which is ironically probably making me appear as a different type. Because I learned to socialize using a logical approach that I experimented with over the last few years. Things like patience, being forgiving and accepting, being silly and not taking things too seriously is all learned behavior because I wanted to learn to act that way.
Learned behavior can make someone appear different. I come across as if I'm an Enneagram 9 in many situations when in reality my natural state of being is actually a phobic 6.
I also have learned to acquire a sense of introversion in my behavior as well, but when you peel back the layers it's just my extroverted intuition has learned to love operating in isolation. If I am by myself looking through books in a library, I may be alone and in my head but I'm outwardly focused and engaging with the material and facts I find. Then again, the dominant function is hard for anyone to shut off. Or at least that's what I've read.
As for the whole "appearing to be another type" matter. We all probably seem like other types sometimes.
I could see you as an introverted thinker since the manner in which you describe your viewpoint appears similar to the Ti process as I know it. So, I can see where someone might think ISTP would be a reasonable option. However, I haven't seen any evidence of Se from you, which calls that typing into question. You do strike me as an IxTx type, though the one of those 4 that doesn't fit is ISTJ in my opinion.
Also, I agree that typing can not be done based on political preferences. Unless we want to attribute my indecisiveness on many issues and my blatant refusal to take a side as Ne being flighty. But it's not that, I think it actually derived from my 6 skepticism. And people often expect 6s to be adherents to ideologies instead of someone who is skeptical of pretty much all of them. Type manifests differently in different people. I grew up in a household where people of all political affiliations were criticized and I started to pick up on things like double standards as I got older.
Of course, people are going to stereotype even though I can point to exceptions. An ISTJ friend of mine doesn't like talking about politics, but I've known him long enough to know that he surely isn't going to align himself with the Republicans. Though part of that is probably because he is transgender and social conservatives are known for not being transgender friendly (some are, but a large enough number of them seem not to be).
The rule in my mind is that an individual is the best person to figure out their type. It takes awhile sometimes though.