Why does the government have to get in the middle of a contractor and what contracts he chooses to make or accept. If I make a contract with one company for a period of time,after the contract period ends I can make another contract with the same person/company or another one. It’s my choice, unless I am a slave/subject of the government, then that’s different.
Instead of those employees getting jobs with different companies, they brought this to the attention of the FedGov who wasn't friendly with Bill Gates at the time.
The thinking is that a person isn't allowed to freely choose to be someone else's slave, nor is that person allowed to freely choose to be someone's indentured servant.
Contracting for a single company for an extended period of time and not being treated as an employee appears to some people as a form of indentured servitude.
You may disagree, but FedGov is becoming all powerful. If all you have to do is run a few jobs for some other shipper, rather than hoping that you'll get your way via the courts or some form of work stoppage, then maybe that's a better alternative.