1. They care because they're paying for it.
2. This is a straw man argument. I did not say what you are accusing me of saying. Anyone can read the post you are responding to and see that I'm correct.
I didn't say they would force a nurse to do anything. In fact, I explicitly said that they wouldn't instruct doctors to do this, and I'll say now that the same goes for nurses and all medical staff. Directing employees away from treatments doesn't have to be so heavy-handed as forcing medical staff to do anything: I explained how they could go about this more subtly in my post. I'm open to you criticizing my posts, but I do insist that you critique what I've actually said.
To expand a bit, this could be as simple as writing the informational materials on each of the services they provide, placing negative side effects more prominently for treatments they want to discourage. It's very hard to accuse anyone of wrongdoing if they put side effects for one treatment in red on the front of the pamphlet, and hide them for another treatment in 6pt font at the back of the pamphlet, but these sorts of strategies have real-world affects on people's lives.
3. I may be misunderstanding the article (and it's currently down for me, so I can't check my memory), but my impression is that this clinic is paid for by Amazon directly, so that employees won't have to go through their health insurance for basic treatments. Ostensibly this reduces the cost of health insurance. But it's highly unlikely that Oasis bills Amazon one opaque number and Amazon just writes them a check: Amazon (reasonably) would want to know what they're paying for. And once you know what you're paying for, that gives you a lot of information about your employees. For example, filling prescriptions is one service provided: if there is a line item for Rilpivirine the employee probably has HIV, if there's a line item for Disulfiram they probably are an alcoholic. They don't need full access to medical records--merely having access to medical billing gives them a lot of information which is inappropriate for an employer to have access to.
You're casting these possibilities as if they're conspiracy theories, but these are all things which health insurance companies already do, particularly the first one. The incentives are slightly different for Amazon, but it's not outlandish that when they start taking on some of the responsibilities of a health insurance company, they would also pick up some of the abuse behaviors of a health insurance company.