This article is a bunch of crap. There is no company that is capable of making me train anyone. ( unless they don’t tell me, of course. )
Go home tell your wife you got laid off and you REFUSED severance pay. See how well that goes over.
It's more of a bribe. Train your replacement and you'll get severance and a good recommendation and can collect unemployment. Don't and you are fired for insubordination and can't even collect on the UI you've paid into all those years. But you are correct, nobody can FORCE you to choose the former over the latter. A private person doing this to another would be charged with extortion, but what the hey.