Another rather substantial difference is in M2 matrix of Oklab. In my experiments I don't see S-participation in colors with high spatial frequency. Because in image compression a lot of information is in high spatial frequency, one gets favorable image compression when M2 matrix is without S contribution in Luma. We use just [b b 0, a -a 0, -0.5 * c, -0.5 * c, c] in the M2 phase in JPEG XL. The two 0s there don't bring S reception into Luma and redness-greenness observations.
This difference can be because Oklab is based on XYZ which is based on 2 degree color samples. XYB is based on about 0.03 degree color samples. Perception seems to be different there -- to me it looks like S is not yet integrated into Luma experience at that resolution.
In butteraugli color modeling is more complex: it is divided into high spatial frequency and low spatial frequency. S is brought only to the low spatial frequency color transforms. (Frequency separation there is by Laplacian pyramid.)
This difference can be because Oklab is based on XYZ which is based on 2 degree color samples. XYB is based on about 0.03 degree color samples. Perception seems to be different there -- to me it looks like S is not yet integrated into Luma experience at that resolution.
In butteraugli color modeling is more complex: it is divided into high spatial frequency and low spatial frequency. S is brought only to the low spatial frequency color transforms. (Frequency separation there is by Laplacian pyramid.)