I think the “key” to understanding Pointer gamut is within the equation for converting spectral reflectance to XYZ. That is, you multiply the illuminant by the reflectance curve (to echo a few posts above). The illuminant is therefore the exchangeable ingredient that makes the surface color. The reflectance curve is the true identity of the material and static for a given object regardless of the illuminant.
We can experience objects under an infinite variety of illuminants. If you did a union of ALL the color perceptions for real world diffuse objects under every potential illuminant (including lasers). . . you’d have a gamut very close to the entire CIE chromaticity diagram.
So, the Pointer gamut is most meaningful in the context of Illuminant C, which is why the Li paper above, and Meng (and others) are trying to create a new gamut of real surface colors based on spectral reflectances. Maybe Li will have something to report to the CIE soon? It’s interesting to see how the CIE organizes their projects.
Still, I don’t know how useful a single gamut of “real” colors (spectral reflectances, rather) will actually turn out to be. It might be far more useful to have a database of “real” spectral reflectance curves for particular materials. This paper describes such a system. It would be a lot more work, obviously. . . but allow you to have believable surface colors for wood, concrete, common cosmetics, particular types of paints, etc.