Another observation of last picture above: Although both beams as a result of the lower CCT (4000k and 3500k) are “warm” in nature, the “tints” are clearly different (one is green, the other rosy). And IMHO the tints are different likely because the 2 LED’s have different Duv (the other factor besides CCT, that affects “color” of a beam).
If I have to guess, it would be that SST20 is above the BBL line (positive Duv, resulting in greenish tint), whereas Nichia 219b 3500k is below BBL line (negative Duv, resulting in that rosy/magenta tint that is so loved by flashlight hobbyists).