Dear Bill,
SG contains a set of patches that are very close to CC24 ("24 patches from original ColorChecker", "the corresponding patches are laid out on the SG chart in the same configuration as in the standard ColorChecker"). If one wants to be very accurate he can replace the Passport spectral measurements contained in X-Rite profiler for ACR/LR with the respective values from SG.
Now, if "classic" part of SG is used in X-Rite profiler, and the error is computed using all other SG patches one can evaluate the accuracy of profile in a more reasonable way.