Most people misunderstand the reason for flushing. Flushing will not remove nutrients that are already inside the plant. It only removes extra nutrients from the soil or growing medium. you do not need to flush at all if you haven’t been trying to max the nutrients the whole grow. Do you think outdoors growers have been flushing for the thousands of years marijuana has been grown outdoors? No, the indigenous peoples’ traditional way of growing never required “flushing”. Flushing is to starve the plant, so it is forced to use the nutrients stored in its tissues, leaves, etc. The whole process is to reduce chlorophyll. It is part of the “curing” process.
Placing the plant in the dark will not necessarily increase trichomes. The plant will produce about the same amount of THC in those three days as it would with the light on. Actually maybe it will make more with the light on as it is still using the chlorophyll to process the light and power its metabolic functions. However, at the end of the grow when the THC production may be at an end anyway, the three days in the dark will force the plant to use up some of the chlorophyll, possibly making the rest of the cure easier or shorter. the cure itself is to try a get rid of some of the chlorophyll.
The plant is not totally dead just because you cut it off and put it in a air tight container/jar in the dark. Just like a rose cut off and put in a vase with water is not dead and takes days to wilt and die. Putting a not totally dry bud in an air tight container makes the still live cells in the bud’s tissues continue to process some of the nutrients/chlorophyll, some may be processed into THC, but it will certainly reduce the chlorophyll and make the bud smoother as a result. potentially some good microbes (not mold) will also break down some of the chlorophyll and contribute to the cure and smoothness of the bud. This is why the longer you can keep some moisture in the curing bud without it staying too moist and molding, the better the cure. The cells in the tissues of the buds and the microbes need the moisture to continue to live and process the chlorophyll and nutrients still trapped in the buds, this is the only reason for light depravation and nutrient depravation during the end of the growing/curing cycle.