Regardless of one's experience or lack of it with a particular presentation, conscientious, safe, and proper care decisions are not made on guesswork—not when there is an easy and readily available alternative. And I'm sorry, but "I don't see many cases of this" isn't a valid reason for taking chances.
The fact remains that administering insulin to someone who is low is dangerous, potentially fatal. If someone knows enough about diabetes to know that unconsciousness is a possible "symptom", then they had better know that there are not one but two ways it can happen, and a very simple real time test that takes only seconds will immediately tell you which one you're dealing with.
If a medical professional has ready access to insulin and the means to deliver it, but not the means to do a simple finger stick, something is terribly terribly wrong.