It's my understanding that molasses feeds the microbes in the soil that "tend" to the roots. There are some trace minerals but the major benefit is the sugars and nutrients to feed the microbes in the soil. The microbes break down the soil for the roots to absorb, basically.
It can be given throughout the grow.
Now giving molasses towards the end of flower has all sorts of reasoning. One can go on and on with all of the theories. But it is similar to the bud fattening products, basically sugars. Sugars the plant uses to bulk up the flowers. This is all in theory, I don't know all of the science behind it. Personally I think it's the microbes the whole grow. Hope to have helped some.
Californiakid