When we learn about MBTI we learn or make our own techniques of typing others. Many new to MBTI prefer giving a typological profile to people based on what they have learnt through the definitions of the preferences or based on the stereotypical perceptions of certain type profiles in their minds.
Those more knowledgeable about the topic would look towards the functions and would try to adhere people to what functions they use. Both, if done with correction, may work to a degree to help typing people.
What is it you tend to do and/or give more credit to and why?
My personal process is typing by preferences and then adhering the person to the functions of the type I believe they are. I would think the explanation of the Judging preference doesn't always adhere to the first functions of what we think the person is so either it may contradictorily confuse us or make us almost certain they are that certain type if the first function of the person works in parallel with the definition of the preference. This would be based on the person's perception of it.