One of the important and unintuitive points is that this is exactly NOT true. The extra hours are NOT free to the company. Ok they don't pay for them in money

One of the important and unintuitive points is that this is exactly NOT true. The extra hours are NOT free to the company. Ok they don't pay for them in money, but also don't gain anything in additional work being done. In the extreme case they loose productivity, people get sick, people quit etc, which is a very real cost for the company.