I didn't understand your point. Could you explain with more details?

In order to obtain information regarding substrate in use at any point in time during exercise we use RQ. In order to determine the precise absolute and relative amount of that substrate we use stoichiometric equations. Therefore, these two are causal connected but are not the same. 

It is quite interesting! If I understood correctly, RQ is a general estimate of global state of substrate consumption. It is blind to more precise and accurate measurement indeed. It seems to me that FATmin and RQ estimates different points of the same phenomena: RQ a most external and global indicator and FATmin a more direct substrate consumption indicator. Most than causal relation, I think that both measurements take different point of the same process. When we have a resting body RQ and FATmin are equal, but after exercise, e.g., RQ indicate more that just a FATmin state but add recovery and anaerobic global effects. Is this reasoning accurate?

During and after exercise RQ is a also an indicator of fatigue or better said effort of the person. If person goes above RQ= 1.15 its means that the person has given all out and the exercise is maximal.

You are not quite right, FATmin (determined via stoichiometric equations) and the RQ =1 should estimate the same point of the same phenomena: minimal fat utilisation point. However, minimal fat utilisation point determined via FATmin and via RQ of 1 is not always the same. They are highly correlative but sometimes they differ. 

Why?