Socionics is a model of information metabolism. Yes, it relates to people and is mainly used as a personality theory. The model A though was created based on Kepinski though, making it a component of information processing.
Idiotic Rational Points made
1.) Everyone uses every function in Model A. Yes this is true to an extent, but model A shows the information and how it evolves its way to the ego process and back to the subconscious(note it doesn't exactly have isolated stages). As I have said before, you don't use your 7th and 8th functions to mop floors or have fun at parties; and yes... people do use other functions, but remember that we are dealing with a model, not actual people... but this deals with people, not the model. People can't be perfectly modeled, and quite frankly socionics doesn't come close. It is almost like some people are making others into a model, instead of trying to use the model to understand different wavelengths of things. People aren't going to fit directly into perfect little categories.
2.) Statements like "Si is about observing the relationships between objects" and "Se is about observing the static properties of objects".(and yes sweety this is aimed at someone) You have just named two traits that exist in every single human being. Existence in itself requires these two traits. As a matter of fact, I'd go as far to say they are the same damn thing. You can't observe the relationship between objects without knowing the static properties of something; and the static properties of something are just the result of interactions of objects. Saying that these two concepts are conflicting categories is a paradox; they go hand in hand, always. Usually when trying to explain this to someone I'll get the response "All people use every function". I usually find this very cute and aloof; tee hee. When we talk about Si and Se, we aren't talking about people; we are talking about a damn model. A model, its a mother fucking model. A model mother fucker. If the model overlaps and is paradoxical, then what is the damn point.
I'm tired, and I have other points I'll get to tomorrow.