This is why people do it = supposedly, the increased dark hours puts the plant into a state of biological panic as it associates darkness with winter (and therefore death). The plant wants nothing more but to make seeds before it dies, so it produces trichomes and terpenes to attract pollinators and catch any passing pollen more effectively. In the "Bro scientist" mind: the act of putting it in darkness for 48 hours should therefore increase the THC and terpene content in the plant just before you harvest.
However, I have done this myself for many years and listened to all of the Bruce Bugbee lectures etc... I still honestly couldn't tell you whether it had any effect at all. I did read recently that it may increase final THC yields by something like 0.2%, but it's another one of those things that needs more research from actual scientists.
Years of stupid laws and persecution against growers has put cannabis growing back a hundred years in comparison to the amount of scientific research available on growing hops and making beer. And why wouldn't they research that? All in pursuit of getting drunk so you can go out and have a fight on a Saturday night, or run some kid over, but you couldn't mind your own business and grow a naturally occurring plant. Good job, Nixon! Your "war on drugs" shall be remembered and we will spit on it's grave and yours!
Yes it sounds feasible from the "bro science" stand point, but nature doesn't necessarily work how "bro science" wants it to. Test it and see for yourself - I certainly don't think it made the product worse, I just don't know whether it actually improved it.