If you didn't catch the subtlety of Besoeker's response:
There are multiple ways to change the maximum frequency limits of the VFD output. If they changed the maximum frequency by using the V/Hz selection process, then they are telling the VFD to reach maximum voltage at maximum frequency of 120Hz. So let's say it's a 460V motor so the motor's design V/Hz ratio is 460/60 or 7.67:1. By using the V/Hz pattern programming to change the maximum frequency, they are saying that the output of the VFD reaches 460V RMS at 120Hz instead of 60Hz. So that means that the motor V/Hz ratio becomes 460/120 or 3.83:1. Since torque is directly related to the V/Hz ratio applied to the motor, you are only able to produce 1/2 the torque the motor is capable of. And since HP is a factor of torque and speed, you are essentially at 1/2 the HP at 60Hz compared to what the motor is capable of, but you have full HP at 120Hz only by virtue of having twice the speed.
If on the other hand they left the V/Hz ratio alone for max. V at 60Hz and had simply programmed the maximum allowable frequency to be 120Hz, then what you happen is that the VFD output would remain at 7.67V/Hz until you got to 60Hz. But after that you would be dropping it and by the time you got to 120Hz, you are back at the 3.83:1. So you are reducing the HP at 60Hz and under while maintaining full torque, but above 60Hz you are remaining at a constant HP while losing torque. So you can have one or the other, not both.* But when operating at 60Hz and under, everything would be normal.
*There is a trick though.
If you have a dual voltage motor, you can strap the motor for the lower voltage but feed the VFD with the higher voltage, then program the VFD to reach the lower voltage at 60Hz and the higher voltage at 120Hz. So you end up with a 230V motor, who's V/Hz ratio is 3.83:1. This allows you to have the same feature of having full torque up to 60Hz and then allows you to continue increasing the output voltage beyond that so that you end up with full torque at twice the speed (and thereby twice the HP). The VFD has to be twice the size, there can be no issues with cooling (the motor will run hotter) and the motor bearings have to be rated for the speed. Not for the faint of heart or the novice.