The affirmative defenses from the person whose name they're trying to get suggests that that law is clearly being abused and has no relevance here, which makes me wonder if someone within the DoJ is intentionally trying to throw the case. Let's hope so!
Could be.
But it could also be the case that the DoJ's lawyers just suck. The DoJ has suffered a massive brain drain of competent attorneys since Trump took office last year. First, they explicitly fired or otherwise drove out anyone who'd gotten tapped for the massive and complex January 6th prosecutions. Then they made clear that loyalty to the president had to take precedence over ethics, legality or morality, and that they would fire any attorney who balked at doing something just because it might get them disbarred, all the while making everyone wonder if at some point the administration was going to begin flatly refusing to obey court orders (they haven't, quite, not yet).
That made all the competent and ethical lawyers leave, as well as many who might have been more ethically flexible but were too smart not to realize how badly continuing to work for the DoJ could burn them. To try to fill the massive vacancies, the DoJ then began a hiring spree, openly advertising that no real qualifications were required, beyond a law degree (any law degree) and loyalty to Trump. You can bet that they mostly got what they asked for.
If that weren't enough, the administration also took innumerable illegal actions that spawned rafts of court cases. Many of these were generated by ICE's misbehavior, but there were lots of others. Given the badly-reduced staff, quantity and quality both, this led to the remaining DoJ attorneys being massively overworked. Like Julie Le (who has since quit) who, when faced with a frustrated judge asking why Le came into his courtroom unprepared in a futile attempt to defend indefensible acts, asked the judge to please hold her in contempt and throw her in jail so she could get 24 hours of sleep.
And if all that weren't enough, the continual abuse of the court system by the administration has led to the judges near-universally deciding they have to treat the DoJ's lawyers as untrustworthy, making their lives that much less pleasant.
Given all of that, any DoJ attorney who has a shot at making a living in private practice, i.e. any of them who is any good, has left. What remains is a group of massively-overworked incompetents.
And if you wonder if the DoJ attorneys weren't always incompetents, because clearly the government doesn't pay as well as private practice... in fact, no, they weren't, because the work was considered quite prestigious. In particular, being a US Attorney was extremely prestigious. It has long been very common for talented lawyers to spend a few years in the private sector, making enough money to set them up for life, and then quit and go become a federal prosecutor. Because working for a high-priced law firm and making a lot of money makes you rich, but it doesn't carry the same sort of prestige as being a US Attorney, and then maybe a federal district or even appellate court judge.
But all that has ended. So, yeah, it could very well be that the government is making crap argument based on the wrong laws because their lawyers just suck. And also because there aren't any actually good arguments available and the lawyers are just throwing out anything so they can tell their bosses that they're pursuing the cases vigorously.