Ah, the behaviorist approach. Totally valid.
The only problem with your approach in my opinion is that you shove people into boxes. Yes, everyone says this. But the thing with functions is that you can explain differences within one type by different functional weights.
And plus, I've definitely come across people that don't at all fit the prototype for their type. I'd like to think of myself as an example, but there's no reason you should believe me.
I'm just curious, what would you type me as if I didn't have my type listed? Or would you hold off because there isn't enough information? Do I look like a "normal" INFJ?