Well, the article was not being explicit about how supply elasticity was being measured. Given the lag from the spot price to the creation of new production as you point out, the spot price per se is not really the price metric of concern. Rather, it is sensitivity to expected future prices which matter. The question is whether producers get their price expectations from the futures market or from their gut so-to-speak. To the extent producers are hedging new production to lock in sufficient return, then there will be real price sensitivity to the futures market. This at least is quantifiable; whereas price sensitivity to gut feeling is not. So this is how I'm inclined to interpret the idea that producers are becoming more price sensitive.Silliness.
Oil supply is elastic wtih a *time lag*, which is only partly buffered by storage. If demand goes up this week, supply goes up two years from now. This predictably leads to swings up and down (it's easy enough to do the math to show that this always happens). The only way to reduce volatility is for the *time lag* to go away (not happening) -- or for a cartel or regulator to fix prices or fix production.
Oil demand is of course more elastic than before, and with a shorter time lag than supply. That does mean that we should see recurrent gluts in oil, but the price will still swing.
A futures market can reduce volatility. Or more accurately, it transfers market risk from producers to speculators and other traders. A robust futures market makes a cartel less important.