I always chop at first light of dawn. I've read terepines evaporate in the sun and then reproduce over night. (no idea if this is true) but that chart makes me think that is probably correct...
I also think that the plants natural osmotic flow would be minimal early morning. Theoretically, there should be less sugars and starches from the soil flowing to the plant at this time.....(sugars and starches are acrid tasting when burned)
HOWEVER, I do believe a proper cure will convert those elements anyways, leaving you with good, clean tasting bud.
So, I guess it comes down to science, and you would need major controls and samples to get an accurate idea of time of day effect on harvest (terepene profile, length needed for dry/cure, potency and the effect of chemical ratio make-up(THCa, CBD, CBN, etc), longevity of storage and its effect on degridation of individual chemical compounds).....you get the idea.
Until then, I think it's up to individual experimentation and preference as to how, why, and when you chop.