The article actually goes on to address this specific point:

  Of course, in practice, richer workers are able to negotiate for both paid vacation and paid holidays. It’s poorer workers who can’t take any time off. This table shows how it actually works out across the economy.

While the top wage earners seem to be able to negotiate comparable number of vacation days as most other nations, it's the bottom wage earners that seem to have absolutely no negotiating powers.