you know its kinda hard to test a tert function from a person who havent developed it at all yet. when you ask something, its never 100% sure from what function the answer is coming. also its impossible to say from what position the function that answers is, but its usually one of the strongest functions, because strongest functions are the ones that are most likely used.
i dont think its a good idea to try to find lack of function usage when typing people irl, because some functions are pretty much impossible to notice. so if you look at lack of functions, there will be lack of function perceived that is actually being used. now ofc this can be used as a pointer towards a type, but there are many more efficient/reliable ways to type people irl. like think I-E, N-S, T-F, J-P and if you see like clear E and T, but not sure about S-N and J-P, then you start to look at what functions are used, for me its easier to figure out the orientation of functions, so i would be looking at J-P, by looking at Te-Ti, at this point its also good to look if there is signs of Fe, Fe would suggest towards ETP. lack of Fe shouldnt be thought as ETJ tho, because some ETP people just wont show or havent developed their Fe. and once the J-P is decided, lets say it was J, so the person is most likely an ETJ, now its easy to look at P function, because you are more certain it is I, so you just have Si-Ni to decide. but its important to be able to go back on your deductions, because if you cant match Si or Ni, it might be that the Te is coming from tert or auc function, and that would fuck up the whole type, or it might even start to look more like Se+Ti...