By the time I'm done training, supercropping, accidentally breaking stems, and otherwise torturing my plants - their stems are well scarred and knuckled up as well. Not sure that it makes any difference to yield - but it does strengthen stems where they need it.
By the time I harvest a plant, it's done growing. It's leaves are yellow and dying down like a tree in the fall. Buds are ripe and gooey. It's not drinking water, it's not growing. It's drawing what's left of the energy from its leaves. It's ripening a little. Most of its functions are shut down.
So if I go damaging the stem at this point '3-7 days before harvest'- how is that going to cause a '20% increase in thc'. Where is this thc supposed to come from?
Thc is created in the flowers by photosynthesis and my plant has had on average three months or more of healthy flowering time in which to do this. Now it's winding down and most of its foliage is finished and the rest is definitely compromised in its ability to function.
Jamming a stick through its stem doesn't seem like it's going to work any miracles. Not saying it's not possible- but it would be nice to hear some evidence, or some better science than 'splitting the stem causes stress and forces the plant to produce more trichomes'. Hmmmm.
The dark period has been cited as maybe helping boost the terpenes. Meaning that the plant might have increased smell and flavour.
Another theory is that, since light degrades thc (apparently true), then you'll harvest the plant at a time of maximum thc. Apparently the plant plays a constant game of catch up as thc is produced, but degraded by the lights at the same time. Seems that no one has ever done any lab tests on this - or if they have they haven't shown any difference, because people are constantly raising the subject and nobody is ever sticking their head up to confirm that there is a measurable difference when plants are put in darkness before harvest.