Modules but not extensions

Hi,

v9.6

https://www.postgresql.org/docs/9.6/contrib.html says " some of these modules are not "extensions" in this sense, but are loaded into the server in some other way, for instance by way of shared_preload_libraries. See the documentation of each module for details."

So I looked in https://www.postgresql.org/docs/9.6/adminpack.html but it doesn't mention how it's loaded.  https://www.postgresql.org/docs/9.6/auth-delay.html does, though, say that it must be loaded using shared_preload_libraries.

Does this imply "silence means it's an extension"?

Thanks