Plants run like a factory with a day shift and a night shift. Productivity ramps up quickly at the beginning of a shift then slows to a crawl over time.
Night shift restocks the raw minerals in the leaves and stems. Gathers up the extra glucose in the leaves and puts it where it is needed. As it works it slowly releases a hormone that induces flowering. It takes roughly 6 hours to complete its task for the night of cleaning and restocking. At 14 hours of night shift everything is completely reset, glucose used up and hormone production crawl to a stop.
Day shift start the day consuming the flowering hormone like morning coffee then sips on it through the shift. It franticly converts the neatly stacked raw materials into glucose. Glucose is produced faster than it can be hauled off to other parts of the plant. Leaf swells with glucose (praying), leaving less room for new raw materials to enter the leaf. Glucose production get slower and slower. After 18 hours it looks like Walmart after a black Friday sale and production slows to a crawl.
So less than 6 hours of dark, day shift is less productive. More than 14 hours of dark flower hormone production is insignificant. Day shift showing up for a few minutes at night will consume a bunch of the flowering hormone and go home. Less than a 13 hour of day is not enough to consume all of the flowering hormone. More than 18 hour days glucose production is insignificant. Minerals are stored in the roots, stems and leaves not the flower. Therefore flushing or when you harvest has no effect on bud mineral content, just the sugar leaves. End of the day minerals are at the lowest and highest glucose.