From the opening page

The Court has long had the equivalent of common law ethics rules, that is, a body of rules derived from a variety of sources, including statutory provisions, the code that applies to other members of the federal judiciary, ethics advisory opinions issued by the Judicial Conference Committee on Codes of Conduct, and historic practice. The absence of a Code, however, has led in recent years to the misunderstanding that the Justices of this Court, unlike all other jurists in this country, regard themselves as unrestricted by any ethics rules. To dispel this misunderstanding, we are issuing this Code, which largely represents a codification of principles that we have long regarded as governing our conduct.

So...

1. Why, if you think the code that applies to all other federal judges is good, did you not simply adopt it?
2. So the problem is that people think the justices consider them not bound by ethics rules because they don't have a formal code, not the behaviors of certain justices that have come to light in recent years, got it.

To me, it feels like this is just written confirmation that they functionally have no code of ethics. They've been dodging the question for months, so I guess this is progress?