This is just apologia for Starbucks' core capitalist nature.

At some point your supply chain transparency breaks down, how ever many steps of outsourcing deep that might be.

No? If you restricted your purchasing to people growing coffee in specific areas with a high degree of oversight and frequent audits, this wouldn't happen. The coffee would cost (them) a lot more, of course, but it's certainly possible to do this.

The point is an oligarchy could incentivize high worker wages and ethical business practices through lots of mechanisms, the primary one being "pay more money for your supplies." They don't. We should be burying all these companies in the grave.