Now if i said that a certain time is equivalent of some frequency, that is 1/time, and its just to figure out an idea, if all the periods will be just like that (leaving offtime aside for now, for judgemental perspective). And suppose we drive the motor with your specs at 1.2Khz, it will reach 0.5A mark every time. We could also drive it like 20Khz instead, but in this case the time period is much shorter and then the current will never have enough time to reach 0.5A. You can also compute that with same formula using t=1/20khz, and you will see that I(t=1/20khz) = hardly 0.02A which is like 20mA and also, interestingly that is the peak, whereas the average will be even lower. So the motor would have no power really with 20mA *peak* current.
I think you take the holding torque number in the datasheet as a "given". By all means that is not a "given". Its a maximum, and maybe sometimes too optimistic. Sometimes its even inflated by manufacturers which specify constant current, as in the coils would be driven with resistors like 30 years ago, which is sort of false, because the coil current nowadays is anything but constant. And ofc when making average, the constant current is going to win over a waveform with same amplitude but which has ups and downs. The constant current will have no valleys, no empty spaces in its waveform, so its already more than double. So again, that torque number being a maximum, perhaps over optimistic even, whatever torque you are going to get it is not going to be that number. Depends on how you drive the motor. Thats why the driver and the motor need to make a good pair together, and there are quite a number of parameters to fit.
I think you take the holding torque number in the datasheet as a "given". By all means that is not a "given". Its a maximum, and maybe sometimes too optimistic. Sometimes its even inflated by manufacturers which specify constant current, as in the coils would be driven with resistors like 30 years ago, which is sort of false, because the coil current nowadays is anything but constant. And ofc when making average, the constant current is going to win over a waveform with same amplitude but which has ups and downs. The constant current will have no valleys, no empty spaces in its waveform, so its already more than double. So again, that torque number being a maximum, perhaps over optimistic even, whatever torque you are going to get it is not going to be that number. Depends on how you drive the motor. Thats why the driver and the motor need to make a good pair together, and there are quite a number of parameters to fit.