Selecting illuminant does affect the aging results. Color assessment depends on the measured sample reflectance and chosen illuminant (illuminating the same sample with different light sources results in different color seen by the human eye). Choosing the illuminant means assuming that the sample is illuminated with illuminant light (beside the fact that the sample reflectance is measured using LED source chosen in MFT). Color difference in time may differ for different illuminants.
We are now preparing some materials to explain this issue in more detail.
Sure, it is possible to enable choosing averaged aging curve as a standard - it is not available now but can be provided in the next release.