Yes, all of what you wrote is true. The sensor makers were geared to human vision: human eyes are most sensitive to green light. In Bayer patterns, the pixel ratio of R/G/B is 1:2:1, and in Fujifilms X-Trans Sensors it is even 2:5:2. So it is logical that integrations appear green when STF is applied with option 'Link RGB Channels' enabled. If you disable this option, the green cast is mostly removed in the displayed image, but the data will not be altered by using this option.I presume the sensor makers have their reasons; and we can't fault PixInsight for delivering the data that's on the sensor, for us to color-balance afterward as we wish. Unchecking "Separate CFA" does allow this effect in the flats to cancel out the same effect in the lights, but I am not sure it gives a better ultimate result.