Why are there deltaE values with Absolute Colorimetric?

I’ve noticed that when I load an image, and plot vectors using absolute colorimetric, I often see the plot values change, even when the destination color space completely encloses the plot data values. Why would that be? I had thought that any value that is in gamut would not be changed (deltaE = 0). deltaE values I’m seeing for points that start inside the destination color space range from 0.5 - 4.

I’ve tried this with a number of destination spaces, and this happens with most, but not all. For example, choosing Adobe98, or my monitor profile, or a printer profile, I see changes to the data values that I wouldn’t expect. The one case where I don’t see any changes inside the destination space is with a 2nd printer profile generated from a different source from the 1st one.