Why is the calculated rated current for this motor different from that on the nameplate?
$$P_m = 75hp \times 746 W/hp =  55,950W$$
$$P_e = \frac {P_m} {\eta} = \frac {55,950W} {0.936} =  59,775W$$
$$I_{Line} = \frac {P_e} {\sqrt {3} V_{Line} cos \theta} = \frac {59,775W} {\sqrt {3} \times 380V \times 0.859} = 105.7A$$

106A is not 124A.  Typically all the performance data (voltages, currents, efficiency, pf, torque) apply to full load conditions.  The current does not.

Stated frequency is at 50Hz, but the motor is a VFD with 6Hz to 60Hz operation.  

At 60Hz, motor will spin 20% faster (n = 1800rpm).  Torque should drop off if motor was designed for 50Hz, but it could be constant to 60Hz.  If we assume torque (T) is constant, increase should provide 20% more hp.
$$P_m = \frac {nT}{9.55}$$
Do the current calc with 20% more hp, you get 126.9A, which is much closer to 124A.  Difference is probably due to changes in pf or efficiency.

To be honest, without input from manufacturer, this extrapolation is just a guess.  

You must also factor in the 209A and 104A currents, off to the right of the 6Hz-60Hz.  Do these currents apply to 190V/380V and at what frequency.

You can probably learn more by looking at how the VFD is set for this motor, but very hard to guess from nameplate.