Yes very true. Especiqlly in the case of acceleration and speed.

In the case of power(hp), torque and rpm, this will apply as well, with area under the curve, as all 3 are correlated.
Edit: That is if we plotted 2 variables on the x and y, with the 3rd variable as area under the curve. But the power run plots are rpm vs torque and rpm vs hp.

In the sense of Load, which can include variables such as boost or throttle position, plus the hidden variables which are not kept constant, such as ignition and AFRs, the power run will invariably have area above the curve.

Trying to go off for drinks Bird.

Will use the leftover brain cells and try to illustrate with a plot tmr.