You need to offer more details about the application.
Normally if the display shows 100Hz then the motor should be running at 100Hz. That said, there may be physical limitations on the system that do not actually allow it to "transfer" that speed proportionately.
A drive can not increase the torque or HP capability of a motor, at some point they decrease as speed increases.
That said a simple example of a problem could be when the drive is running the motor at the desired speed, 100hz in this case, but the system (a conveyor could be an example) "SLIPS" more as the speed increases i.e. once you obtain a certain speed it is incapable, due to mechanical limitations, to go any faster.