IDG, you are correct.
As odd as it sounds, we sometimes 'pretend' we have less powerful engines (eg derate, but it gets around the max derate rule) to allow us to lift more off shorter runways. Typically it comes into effect on the L1011-500 for field lengths around about the 7000'-8000' point.
Shorter fields than this and we use full thrust, and accept the vmcg limit, and longer fields full thrust when we are less likely to be vmcg limited.
It comes down the the fact that it's a stopping problem, not a going problem.
Weird, but true.