No, that isn't true at all. Workers are often exploited even though they can leave (legally) at any time because their economic circumstances have made them desperate. They take side gigs that they hope will earn them enough to make money because they don't see obvious alternatives.

I've seen this in-person... friend was a single-mom trying to get by. These gigs market themselves in ways that are dishonest in order to get participants. Sure, there is high turnover, but that doesn't make it OK.