Paying for health insurance, unemployment insurance and a host of other fees required of businesses for employees that aren't required for contractors.
The article doesn't mention that detail so you may be right.
Those benefits are based on working certain number of hours (because the benefits are fixed, they can not adjust them up and down based on hours worked).
So basically what this law does is prevent people or employers from having flexibility in hours.
Salaried employees negotiate and get benefits and isn't tied to "hours worked".
There are lots of jobs now listing flexible hours as a benefit.