If I am reading the article correctly, the point of the lawsuit is not that they used AI to make their staffing decisions. It's that the criteria they asked the AI to use to make those decisions directly disadvantaged people who were on approved leave for medical reasons, and whose jobs were supposed to be protected by law.
It's an important distinction. These decision makers delegated their staffing decisions to a bot. But bots are not people. If the instructions given to those bots resulted in actions that violated the law, the decision makers need to be held accountable, I the same manner they would if they made those decisions without AI assistance.