That kind of makes sense as plants store
energy during lights on and would surely
run out after a while.
Nobody would run this experiment, however, when you ask, or do something like the OP asked...
Ask yourself:
"How much better could this 72 hours of dark help my plant..."
It's a 72 hour period of time..
So would your plant be better if it had 72 MORE hours of nice lighting....
Or would it be better with 72 hours of 12/12 ...
No one could ever answer why or which way would be better...
It's like 1/50th of your grow time...
Ask yourself: "Changing anything in my plant for 72 hours...do I think anything done to my plant in a 72 hours block of time will make a difference..."
Answer... Not Really...
At the end stage of your plant, why would anyone... want to mess around...