FWIW, I initially had the same reaction, many of the arguments surrounding the importance of +2 make direct reference to the particular configuration of MediaWiki and extensions Gerrit and Jenkins setups.
Putting that aside, the section on merging without code review feels particularly prescriptive; however, it makes the point towards the end:
For extensions (and other projects) not deployed to the Wikimedia cluster, the code review policy is up to the maintainer or author of the extension.
I think I would prefer if that were easier to glean from an inspectional reading of the policy rather than a close reading.
Also, it's important to note that self-merge is common in some repositories (integration/config for instance), and there may be differences between projects in what exceptions there are to merging without code review; however, in these projects, +2 is still "a strong expression of trust", only the expectations are different.