Do they hire H1B's? That would be a really quick clue as to whether or not they are doing work for NSA. None of my Indian friends know any H1B that works at Palantir, which is really odd, but maybe other people have different anecdotes.
I would not use that for blanket decision making. The technology, just like much of IBM's entity relationship/NORA stuff that you can download via the IBM customer portal, is mostly declassified stuff that has applicability to fraud detection, pandemic/health outbreaks, and plain ole data analysis. Anyone could work on that stuff.
Where you need people with a clearance is to actually touch the data - which means implementing/deploying the software, training their users with real data, and supporting it.