Libtool works on many different operating systems, which behave in various ways. Some OSs will find a new library automatically if it is installed in the existing configured library paths.
The library installed might not ever be intended to be used by the currently executing OS because it is part of new distribution builds.
Sometimes libraries are installed privately, using hard-coded run-paths in the dependent binaries. This is very common when a different version of the software is to be run than the OS is designed to support.
Expecting a libtool (merely a shell script!) maintainer to write such a document is unreasonable. It is possible that GNU has such a document specific to GNU systems.
Bob