This is obviously not the situation under discussion. The book wasn't released before he earned any money on it.

He clearly states "My income dropped almost immediately", which makes it clean that he was earning money from it, and that a specific event—the piracy—coincided with a drop of "$Xk worth of sales" per month.

The analogy being drawn is to losing a job and consequently losing the income you would have earned from it. You've switched from "you never had that income" to "you never had that job".

Thanks! I was wondering specifically about how the logic of “you can’t claim something as a loss if you never had it in the first place” meant that you can never lose a job or source of income, but it sounds like that’s not really what they meant in the post I was replying to.