Thanks for the clarification.
I can see the logic of doing it, just hadn't seen it happen before.
Who ultimately makes the decision? Presumably, the airline would want it done if possible, as you say, five minutes' of flying is a fair amount of fuel at what I imagine would be an "expensive" part of the journey? Climbing straight up must be preferable to turning round 180deg and climbing?
However, there must be important safety concerns too, so is it down to airline ops, the pilot or ATC?