For values >0 it is. ACEScc does not code negative values because it is a pure log coding, with no “toe”.
With ACEScct (or any camera log coding) offset is equivalent to linear gain in the logarithmic part, but is noticeably different where the offset moves values into or out of the linear portion of the curve.
Here is a plot of the curve adjustment needed to match exposure changes in ACEScct. As can be seen, it is a simple offset in the upper part, but very different at the bottom:
