Turobofan's usually are rated for peak power at a certain rpm, the engine used in Nirbhay is a derivative by NPO saturn/raduga okb with lower fuel curve, the challenge was to change the suction port manifold to increase volumetric efficiency of the system, with a smaller combustion chamber for the Nirbhay. This engine I suspect was re-engineered russian engine. So I guess both of you are partly correct.
In which field you work in dude??