You probably missed it because you were only looking for examples of OPEC reducing production. Shale oil used to cost around $80-$100/bbl to extract. As long as the price of oil remained below that price, extracting shale oil was economically unfeasible and oil companies threw just a token amount of money into its R&D just to keep it ready on the back burner. So OPEC was trying to keep the price of oil high, but below that $100/bbl threshold. When the price of oil did drift over $100/bbl, OPEC increased production to try to bring the price back below that threshold, keeping shale oil borderline unfeasible.
I think what OPEC (and everyone else) missed was that you don't just get oil from shale oil. You get natural gas too. And that natural gas is what's turned out to be a bonanza, leading it to surpass coal, and threatening to pass oil as the leading fossil fuel. It's driven further shale oil extraction R&D (I believe its cost is well under $50/bbl now). So at this point OPEC is along for the ride just like everyone else.