I suspect "fake" is the wrong word, maybe "very low reputation" is better. The parent post discusses avoiding giving unlimited free trials to people who just keep creating new accounts. You'll want to restrict that, especially if each trial costs a non-trivial amount of money. Efficiently detecting such abuse allows the company to offer generous free trials.

A side effect is that a small number of people who use disposable email addresses to manage the spam they receive will also be blocked (see other comments). A business looking at this issue may find it hard to prioritize, the group is small, and they can choose to use a non-disposable address if they want to continue.