They could just be doing it to be petty and cruel to "government workers" in general. There doesn't always have to be a genius 5D-chess play. It's very possible the administration simply believes the federal workforce is full of their political opponents and just wants to grief them. A major component of the campaign and their base of support is rooted in cruelty to out-groups, so they're technically delivering a campaign promise to their base by just making people miserable.