But how do you know what your preferences are with any certainty? Preferences are by its very definition something that can be freely chosen or not chosen, which not only goes against the idea that a person has a fixed cognitive function, but also supports the notion that personalities can very much be like shoes that you can try on to see how they fit. I agree with you in that trying to fit within the wrong personality can be discomforting, much like the wrong size shoe, but that doesn't mean that a person has a fixed personality either, or a fixed preference.
I guess my point is that a "sensor" or an "intuitive" has a preference for either sensing or intuition, but because it's a preference, it can be freely chosen or not. This means that a "sensor" can be an "intuitive" depending on what they prefer at the moment; the reverse can be true as well. Now, if you consistently prefer intuition at the exclusion of sensing,then yes, you are mostly an intuitive. But, if that's the case, are you really preferring it? If you aren't preferring it, then what is causing you to behave as if you are? However, if you prefer sensing only 50% of the time and intuition the other 50% of the time, you are neither a sensor or an intuitive, but only one or the other depending on the situation.