The approach you took at the end of your grow is a bit different to what was studied
SoOrbudgal From what I understand your approach is not too dissimilar to how most outdoor grows are managed start to finish re watering. Just enough to wet the soil without runoff and as we know runoff strip's soil of nitrates and other goodies plants need.
Firstly you were growing outdoors in a soil of types, so it's producing its own nutes and keeps producing them as long as the soil contains moisture whether the plant is in the soil or not.
Secondly you roughly monitored your plants water uptake and reduced the water you gave it in line with the plants needs. The last week of a plants life it needs very little as its no longer growing and just trying to survive to reproduce, a last ditch effort at maintaining the species...evolution at work! It's also cooler and rains.
This still allows the plant to uptake its nutes it needs to survive, particularly the nutes that are immobile and locked into the plant cells that cannot be transported to the buds to keep the buds viable to reproduce.
So your plant still gets the nutes it needs to survive that last bit.
This flushing bit is all about denying the plant pretty much all nutes. Think hydro without feeding it but still giving it water. This kills the plant because it can now only scavenge nutes that are available as mobile nutes in the plant, and denies the plant all nutes that are not mobile. So the plant runs quickly into an imbalance, stresses and then starts to die. The yellowing of leaves is dead plant. Once this happens it's my theory that it is more susceptible to disease because it is now sick.
I know when my sativas are stressed and sick they are more prone to mold and disease and losses go up fast. I harvested last grow early because of this not wanting to risk losing some decent bud even though it was a tad early. If you look closely at my last grow you can see cal/mag deficiency on one almost throughout the entire grow, heat and light stress on many of the buds especially the most developed and other minor problems...plants getting sick very fast.
Edit. During the dry plants continue to transpire they just can't photosynthise so well in the dark. The health of the buds is at its most critical point now until moisture gets down to a level where mould spores cannot take hold and grow. I thinknit best to start this with healthy buds and not buds rotting on the plant.