I have done some research on this subject... I have copied and pasted my findings... You can decide for yourself...
In the wild, cannabis plants are on a very tight schedule. Because these plants die every year, seedlings must emerge from the soil in the spring, grow very big very fast, then pollinate to make seeds in time for fall, when they naturally die off each winter. The seeds lay dormant through the cold winter and sprout the following spring to create the next generation. The cannabis plant uses a special system known as "photoperiodism" to determine when to mature and produce buds/pollen/seeds. Because they have to complete their whole lives in one year, the plants need to time everything right in order to grow for as long as possible during the spring and summer, then makes mature seeds in time for winter. After sprouting, a young cannabis plant gets extremely big extremely fast, and grow only stems and leaves for the first part of its life, kind of like the "kid" stage, since the plant doesn't have any sex organs during this part of the plant's life. As the days grow shorter, the plants "sense" that winter is coming; male plants make pollen and female plants produce buds. The wind blows pollen on the female buds (which have wispy hair specifically made to catch pollen), which pollinates the female plants so they start making seeds. Because of this crazy time schedule, cannabis plants need to keep everything is sync so that the male and female plants produce buds and pollen at the right time, and the female plants still have enough time to produce mature seeds before they die when winter comes. (On a side note, the buds we smoke are the result of female plants which have never been pollinated.) When growers give the plants shorter light periods during the day, this is mimicking what happens in the wild. The shorter days "tell" the plant that winter is coming. In the wild, nights naturally get longer as winter approaches, and cannabis plants use a hormone system to keep track of how long the nights are. When nights start getting really long (days get very short), the plant starts maturing the buds very fast, because the plant "thinks" that winter is coming right away. So to answer your question, when you give the plant shorter periods of light each day, you are causing the buds to mature faster. However, because the plant is getting less light (less time to make energy with photosynthesis) each day, the buds are going to be smaller than if the plant was given the longer periods of light. Also, the plant will mature faster, and so this also reduces yields. In my experience, here are the cases when growers benefit from giving plans shorter light periods than 12 hours during the end of the flowering.....
1. For strains that come from the equator where light levels are often near 12-12 (usually sativa plants) reducing the flowering light period to 10-14 or even 8-16 is sometimes needed to get the plant to mature.
2. Also for some Sativa and Haze strains, the normal flowering period is 3-4+ months, and shorter light periods can be used to "force" the buds to mature faster
3. In cases of extreme heat, sometimes the yield loss from shorter light periods is worth the reduced heat, especially if someone is just trying to get their plants to survive until harvest
4. Any other case where getting the plant to ripen faster outweighs the potential loss of yields, like if you knew you were moving to a new home soon
I normally wouldn't recommend shortening the light periods during the end of flowering unless you have a stubborn Sativa or Haze that just won't finish ripening, or if you have some reason you need the plant to ripen faster. Otherwise, I believe the only real result is reduced yields.