Color devices are not colorimetric. It follows then that some color correction must be done to map device RGBs to XYZ's. One common correction method involves finding the linear transform which takes device spectral sensitivities as close to the XYZ color matching curves as possible
(in the least-squares sense). Thereafter, this transform is used to map device RGBs to XYZs. It is well known that this procedure is statistically justified so long as one assumes that all spectra with positive and negative power are equally likely to occur i.e., so long as one is
Graham D. Finlayson, Mark S. Drew, "The Maximum Ignorance Assumption with Positivity" in Proc. IS&T 4th Color and Imaging Conf., 1996, pp 202 - 205, https://doi.org/10.2352/CIC.1996.4.1.art00052