If the SSA is antyhing like DHS they have to certify with the same rounds they carry on duty. There are all kinds of liability issues for practicing with rounds that are different from normal duty carry. It is probably a violation of service policy to shoot anything other than the hollow points they are issued.
You’re likely right. That doesn’t make it right. There aren’t that many terrorists that the non-military government would need over a billion rounds for. This is planning for civilian dissidents - citizens.