NIF is explicitly and publicly a weapons research facility; it's right there on their website[0]. If they happen to do some useful scientific or commercial work then yay but it's a nice byproduct.

[0] https://lasers.llnl.gov/about/missions/

Actually, the site you linked lists 3 goals. Weapons research is only one of them. The other two are commercial and scientific research. Those are not mere byproducts, but explicit goals of the facility.

They're fig leaves.

He's not saying the facility is a sham, he is simply saying it's goals are not to generate electricity, it's simply a research tool to provide data to improve empirical models. Those models of course have all sorts of uses, and certainly a big one is nuclear weapon modelling.

You say "speculation" as if it were a bad thing.

I could speculate that space aliens secretly landed in Roswell and took over the government 60 years ago, but without evidence, it's just a story.