This is awesome. I referenced cppreference, but that is not authoritative. Unfortunately, in the final draft, [class.pre] grammar makes the name mandatory even though the language you quote remains in the first textual paragraph following the grammar specification!

The part of enums you quoted was C-compatible enums; anonymous scoped enums are explicitly forbidden: "The optional enum-head-name shall not be omitted in the declaration of a scoped enumeration" (dcl.enum 2).

Sigh. I will send in a clarification at least on the class/struct/union side. Ideally the grammar would be fixed rather than that paragraph.

The draft I looked at is https://timsong-cpp.github.io/cppwp/n4868/ (2020-10-18, shortly after the standard was approved).