Yes it's probably true that daylight temperature is not that important for the profile result, I've used free outside daylight so far for my profiles and it seems to work well. It's something I want to test in my experiments though, I do this both for making profiles to use, but also learn something about how camera profiling works and maybe write a little article about my findings.
Since I now have three process versions of Adobe imaging apps CS3, CS5 & LR4.4 and their subsequent updating to their DNG converter and Adobe DNG PE AND what others say about Base Profiles as starting points such as Adobe Standard for DNG camera profiling, I've now noticed the differences applying the old profiles generated using the same daylight lit CCchart in CS3 vs LR4.4 but only to a wide range of legacy images.
The differences vary depending on the image scene some slight and some more pronounced especially the LR4.4/Adobe Standard Base Profile created from a CCchart lit by overcast clouds vs direct sun. But I didn't start noticing these differences at first because the LR4.4 with current DNG PE made the CCchart target image look less saturated (more accurate by the numbers) than the old CS3 profiles that I took that as an improvement. Now I'm finding the hue/sat differences on some images don't produce desirable results and keep reverting back to using either ACR4.4, Adobe Standard or the old CS3 custom single and dual illuminant profiles.
This discovery between these profile versions was an unfolding process so I'ld have to conduct a rigid test to see what was influencing what due to all the variables in order to track down whether the changes are due to the newer updated software, Base Profile in the DNG or illuminant CCchart.
I know for my camera Adobe Standard neutralizes the entire image to appear less greenish yellow which does make the CCchart gray patches look reddish blue but I don't know if the DNG PE CCchart Wizard is removing the Base Profile's influence on WB of the gray patches before it automatically corrects the cast and builds the new custom tables. I do notice this particular Adobe Standard/LR4.4 sourced DNG profile makes images look different than the old CS3 made profiles.