I can't see a plant having any difference in THC or Terpene profiles after only3 days. This is just my opinion, but other than stretching and possible water content variations, I can't see any hard data to support this. Claiming stress is a semi canni-legend, and 3 days isn't much of a stress to a plant. Plants don't "think" they are going to die and suddenly send a rush of everything they have to ward off the inevitable. They live to make seeds and have been selectively bred to keep trying despite not getting pollinated.
Does a 3 day absence of light affect the plant... Absolutely.
Does the 3 day absence of light increase the THC or Trichomes... Personally, I don't think so. That isn't to say I could be mistaken, but I can't see a scientific basis for this to happen in the time period mentioned. Sugars and other metabolic processes would be more affected than the more complex processes needed to make the stuff we like, IMO. I know we have some guys who are pretty spot on about the actual processes that lead to the triggers for increased Trichome and other parts of the plant... maybe someone will chime in that knows a lot more than my conjecture.
Not so much increases of but darkness does help terpene and essential oils for that specific strain Know if you give your plant 24-48 hrs's of darkness this shorten flower time by 1 week