This behavior of legal loopholes to discount workers should be made illegal. The definition of sub-contractor has got to change and/or have laws/policies in place that actually make sense in a sub contractor relationship. These are shell companies that spin up and exclusively deliver for amazon, they aren't gig workers delivering when they want, they have strict quotas.
These aren't contractors like Uber drivers. They are corporations that are contractors of Amazon, and the drivers are employees of those companies. How would this possibly be a legal issue?
This is the same situation when independent contractors have only one client.