Are they buying them or reserving them?
I think they are just trying to keep them off the market by setting them aside so the public cannot buy them. I suspect they did that with ammo.
Not the ones that are the subject of the article. They're all selective fire, meaning they can be switched from semi-auto to full auto at the whim of the user. Since 1986 it's been illegal either to import or domestically manufacture such weapons for the civilian market; they can only be sold to governmental entities. The semi-autos are th ones sold to the civilian market. 9,000 is also a pretty small number to dry up production for the civilian market.
“I think they are just trying to keep them off the market by setting them aside so the public cannot buy them.”
They are select fire so the public cannot own them anyway. Besides, I dont think there are that many sitting on shelves waiting to be sold so they will have to be manufactured.