You are probably right. Those with genuine asthma need to understand the condition and be prepared to deal with it at the onset. My point is that the doctor in our case took a complaint that it was "hard to breathe" on the first and only visit regarding this symptom and diagnosed asthma on the spot, after twenty seconds of listening through the stethoscope. He prescribed an inhaler, which was never used, and voila, we were part of the asthma "epidemic". I think the doctor took the diagnosis far too lightly and that impacts people like your daughter with genuine, life-threatening asthma.
If the "hard to breathe" condition is actually present during the doctor visit, then that would be a perfect time to use the inspirometer to get a reading of the amount of constriction. It is possible that a stethoscope could detect the additional noise that a constricted airway could generate. But the presumption would seem to be that the constricted airway would disappear when the "hard to breathe" condition disappears. Also, the inspirometer permits a quantification of the condition that would be hard to determine using a stethoscope.