But if I was in the Post Office at the back of a queue and another window opened and nobody from my queue moved across (I am always careful not to rush across in these situations so as not to be seen to be queue jumping) I would move over to the queueless window. That is what the unused lane approaching roadworks is - it is a shorter queue to access the same resource.
Your example equates to a single lane branching out to two lanes, which is the opposite of what is under discussion. You should have said what you would do if there were two windows open with even length queues and one window suddenly closed.
At the point of the cones there is a limited resource available to drivers of both lanes - namely the single lane through the roadworks. However, if the Highways agency have supplied two lanes in which to queue to access this limited resource (which does NOT belong to the inside lane even though clearly many drivers in that lane think it does) then I will always choose the shortest queue.
As I have said, scientific studies have already established the correct mechanism for queuing in these situations. Therefore, I can only assume that those so vehemently arguing against two-lane queuing also reject other scientifically derived guidance and thus smoke profusely because it clears the lungs, live under high tension electricity cables because it envigorates the soul and only eat fried food because fat-lined arteries make your heart work harder and that is exactly what exercise does, really.