Because people in highly emotionally charged situations don’t always act rationally. No doubt that is part of the “fun” of being involved in emergency response as a responder.
I want to add one piece of data that nobody yet has mentioned: many 911 systems have the capability to assign place names to their geo-information systems. I used to do computer support for a county-side 911 agency and ours had this. For example you could call and say you were at the 7-11 on Percy street and the dispatcher could enter “7-11” and the system would bring up a list of possible matches. The dispatcher could then select the one on Percy Street or ask for further clarification if Percy was long enough to have two 7-11 stores located on it. So in some places you don’t actually need to know the precise street address.
Isn’t the failure there that the dispatcher did not continue getting information after the first units were on the way? That a unit was not rerouted as the two situations revealed themselves?
If they wait to confirm the whole story before anyone starts driving, some dispatches would never be made at all, and more would arrive a little too late.