For one the thread title says curing but what is being talked about would be in the drying process, not the curing process.
 
Next there is the leave the leaves on so the buds feed off of them during the 3 days of darkness. Dead buds dont really feed. When you hack up a plant into sections of whatever size you cut all natural flowing of everything.
 
What happens then is different substances begin to breakdown, which in most cases is good, but the plant itself is dead, there is no transpiration occurring, nothing is moving from point A on the plant to point B anymore. Expecting that to happen would be like expecting the blood in your arm to keep pumping into your hand after your arm had been cut off.
 
The idea of darkness increasing levels of THC is not something that happens after killing the plant, it happens while the plant is still living and in one piece and still functioning. Studied have been made where, if I remember right 100 female plants were grown and half of them, 50 female plants were given a 72-hour period of darkness BEFORE being harvested and in some strains there was an increase in levels of THC of as much as 30%.
 
Light rays, natural or artificial break down THC. Every day some THC is lost to light rays but during the hours of darkness the lost THC is replenished plus a little more is added so there is a slow continual increase until it maxes out due to genetics or poor conditions that hold the plant back.
 
The basic idea of the 72-hours of darkness BEFORE harvesting is the plants will continue to remain alive but in darkness and there will not be any THC degradation due to light rays but there will be the continual creation of THC at whatever rate that strains genetics will cause it do produce. Making the period of darkness longer isnt of help because by then the plants will begin to die from lack of light so all functions/processes would then stop and the production of THC would stop just like it does when you hack up plants and let them hang to dry.
 
What makes pot more potent/better after a proper drying and a proper curing is that when harvested not all of the THC in the trichome-heads/resin-heads is in a psychoactive form. It needs time to change and to become psychoactive and if properly dried and properly cured you will them allow the THC to become the most potent it can be. So that is what makes dried and hopefully cured pot more potent and not because a dead plant still had leaves close to the buds while it dried and the buds drew from the leaves.