This is because antitrust laws in the US have been reinterpreted by the courts to only apply where there is an adverse impact on consumers. In order to punish anticompetitive behavior that negatively affects workers in keeping with existing precedents, they get into redefining workers as consumers.

That very much seems to be the argument of the companies, doesn't it? Like, "Hey, we're just a tech company that has created a marketplace where people can request rides (for example) and people who want to provide rides can provide them. Both sides are 'consumers' of each others offers."

It seems like normally we see the government agencies bending over backwards to prove that is not the case, that these are actually employees working for the company providing the marketplace software, so this specific word choice in this instance surprised me.

(FWIW, as commentary, I had to insist quite strenuously in my own case that I had NOT been an "employee" of Uber or Lyft, even though I had been providing rides in the evenings when I had nothing else to do when I was new to town and wanted to learn what was cool and meet people. When I got laid off from my tech job, my state government was insistent that Uber and Lyft had also been "employers" of mine for the purposes of determining eligibility for unemployment benefits, until I eventually showed them I had my own LLC, corporate insurance policy, etc., because yeah, I was doing it as a hobby, but I was damn sure going to be running my own business as a hobby, not being employed by Uber or Lyft as a hobby. It's difficult for me to understand why people want to be considered "employees." You're much more at the mercy of the company that way.)

The FTC is empowered by congress with the mandate of ensuring "consumer protection", so if they want to make a land-grab and expand their mandate, they have to twist the definition somehow to make their legal authority nominally cover it.