"dynamic layer" is a concept that is discussed by the community (see google search[0]) but is not present in the documentation.
The documentation has the underlying variable: BBFILES_DYNAMIC[1] but a user searching for "dynamic layer" won't find it in the doc.

Maybe just a note in BBFILES_DYNAMIC section "this direction pointed by BBFILES_DYNAMIC might be called a dynamic layer"? Or a dedicated section outside of the variable glossary?

[0]: https://www.google.com/search?q=yocto+dynamic+layers
[1]: https://docs.yoctoproject.org/ref-manual/variables.html#term-BBFILES_DYNAMIC