Interesting thread, didn't have time to read it all.
I do have once again point out accuracy vs precision.
X-Rite are not going to go into that arena for the CM, nor it's software. What it is doing exactly is not something they would want to let you know.
Yet based on experience, I'd say the second or more iterations on the CM profile are to align grid points to new measured samples to reduce S/N, and sample mean deviation.
Accuracy is a result of the precision of the profile adjusted with more or different grid points, their weighting, etc.
So I could be wrong but I think the iterative profiling adds precision not necessarily accuracy.