On the meta I do think that even having principles creates an opportunity for there to be an explicit in group and out group. A yard stick that you can hold up and say "That's Not Rustacean" or "you're not Good Enough to contribute." While that can be used to curb undesired behaviour, I worry it can be used to exclude more than help.
Which is why it's surprising not to see Inclusivity (yes, with the paradox of tolerance caveat) as one of the core values of these principles. Imo that is one of the strongest values of the community, and it's not quite captured by "Be kind."
Principles are well and good for projects (read: tangible outcomes in the product), like the first section is aiming at, but I am less convinced of utility for communities (abstract and vague, about people rather than things), as does the second section. Maybe it's a bit redundant with the CoC?
I'd also like to see some scoping for those principles, too (not necessarily in the text). The preface is a start, but it's unclear where the principles should start and cease to apply. Are they about the Rust Language project, projects under the umbrella or purview of Rust teams and WGs, projects contributing to "the Rust experience" even outside of these (I don't recall names but there are a few contributor crates mentioned in The Book, for example, maybe pin-project, that kinda thing).
While not directly related, it could be worth to state or restate the mission statement for Rust, not just a foil to present the principles, but as an overarching "this is what we're all working towards, and these principles guide us on the journey" kinda thing. Perhaps every principle should hark back to it, eg "do X, because it works towards The Goal" but that feels a bit overdone.
The case studies make exemplify that every outcome is "a delicate balance", but that "not everything is required" should really be bold and upfront. At the same time, what threshold should there be? Is something that is average in every aspect but very positive in one valid?
More on the concrete side of things, there could also be examples of, say, "wrong moves." Maybe some examples of "red flags" that indicate something isn't quite right, and a design or interaction should be reconsidered.