I found an article on The Cipher Brief describing them: https://www.thecipherbrief.com/defense-neoprime-innovation
Specifically, the idea here is that companies like Anduril, Palantir, and SpaceX are rapidly delivering cutting-edge technology (including software) as opposed to the traditional defense contractor process of long, drawn out, super expensive projects mostly focused on hardware (such as building a new type of jet).
It makes sense: this is basically what happened in civilian tech, too. Delivering high-tech solutions quickly -- dare I say with agility -- is usually the superior approach.