Having toured NIF a few times and worked in one of the buildings adjacent to it a few summers ago, I will say the energy stuff always seemed more like a way to get funding. The main use and aim for NIF is and always has been to re-create some of the conditions inside nuclear weapons and similar fusion-based reactions.

The whole NIF building has the ability to switch modes between classified and unclassified. They wouldn't have gone through the trouble of making this a toggleable feature on the building if they weren't actively using it for both.