Knowing nothing about this other than wha the article says, you are probably correct. Likely to be a pure kinetic weapon, like a “Rods from God” style destroyer. Putting an explosive on the thing would probably slow it down.
Also how would you control something going that fast? I would guess it’s fire and forget. Just my $.02 worth.
We have been experimenting with this technology since 1980. It is a technology that is expensive and hard to control. I don’t know where we are, but what we are doing will not be written up in a popular magazine.
Same with kinetic weapons. Testing has shown that they work, but are difficult to work with. (not accurate and can disintegrate in flight if anything gets off center.)
My guess is that defense against them would need to be of the laser type,— also something we have experience with but mostly is classified.
So I am for taking all this with a grain of salt. We should always suspect our competition to be working with new things.
Control is easy, and it flies a profile that is unique where many considerations with conventional nukes or armaments are irrelevant with the PGS system.