First, in modes 6 and 25 (RGBW + CCT 16 bit), the range values for the tint parameter are very wrong. They are inverted and do not match the ranges in the DMX specification document (link). This probably also applies to all other modes that incorporate CCT, but I personally never use others.
Second, in the same modes, Arri has added a new setting called RGBW Calibrated Color. This allows you to send RGB values to the light, instead of RGBW values, and the light will do the processing to add the white diodes as needed. You can still override the white value, but it is no longer required to mix color. It is not well documented in their manuals (user manual), but it is evident in the gel to DMX value chart they publish where the white value is always 0 (link to file). This setting also allows for a very important feature in the film industry, being able to tune the base color temperature when the color crossfade parameter is max. This is the most important reason I prefer this mode.
Where this becomes an issue is using the color picker or hue/sat controls to mix colors. It always mixes in white, which causes the light to mix inconsistently. I tried editing the patch to remove the white parameter, but this has had two side effects. The hue and saturation controls are completely locked out, and using the color picker gives the same RGB values as if it were still RGBW, just missing the white entirely.
I am working on building my own unofficial profiles for these modes without white, but I would be grateful to have an official one with the calibrated color profile.
