I am not a lawyer, and I am not your lawyer.
Off the top of my head, I can’t really see where or how this is illegal in most US jurisdictions. In “at will” states you can be hired or fired at any time for any reason* or no reason. And likewise you can quit at any time for any reason or no reason. If you can be hired or fired based on this scam, you can be promoted or held back based on it.
Having said that, this is really scammy, and I would not want to work there.
*except discrimination based on: race, color, religion, sex, national origin, age (>40), or genetics. Likewise, retaliation for unlawful sexual harassment.
On the director’s commentary, he states that the ultimate cause of Granger’s illness is deliberately left vague and unexplained. That’s kind of like a plot hole, sort of. Or maybe it’s mystery box, and not a plot hole.