So that should have been the end of it - why didn't the government just do that and leave it there? The gap between the accessible means for them to achieve the requirement they needed and the action they actually took amounts to a harm to Anthropic for which they may have the right to pursue compensation.
Again, you’re ignoring the entire background of this dispute: Palantir. Once DoD has established that Anthropic is an unreliable partner and is liable to act adversarially, they needs a legal mechanism to prevent Palantir (and all companies like Palantir) from taking a dependency on Anthropic. This is what that looks like.
Ceasing to contract with them directly doesn’t change the fact that Anthropic wishes to leverage itself to influence the government. That doesn’t go away. The problem is not with closing all direct contracts between the Pentagon and Anthropic, those don’t matter, it’s with closing all their channels of influence into DoD as a subcontractor.
Similarly to how DoD refusing to buy from Huawei doesn’t protect DoD from their prime contractors buying Huawei gear, they need a supply chain risk designation to ensure they are protected.