I think the Standard mode uses the native gamut and you can only
measure slightly wider gamut with Custom mode because the gamut
readings may show some slight differences with different black offset
settings. --- You may have a slightly less saturated red if the blue
and green TRC has relatively high black points, as R=255 G=0 B=0 will
have a bit green and blue tint too, which is basically the same thing
what CMS engines intentionally do through 3D color mixing to reduce
the perceived saturation...)
