This reminded be of the Planet Money episode on long-haul truck drivers [0]. It's a similar contractor v. employee (company driver) scenario. Not a happy story, unfortunately.
The CARES Act and state-level programs are paying unemployment assistance to contractors and self-employed individuals not usually covered by unemployment [0], [1].
Even DOE is partly privatized both Sandia National Laboratories and Savannah River National Laboratory are run by private defense contractors for the government.
The study examines a factory workplace which may already have a high-level of background noise. Perhaps the effect is non-linear? Anecdotally, two or three coworkers talking near me doesn't feel more distracting than one coworker on the phone.