Hi Gerald;
Currently we offer two modes of database creation:
1) If the superuser credentials are set, then a new database is
created, PL/PGSQL is added to it, and then the database is created
with the normal user as the owner of the objects.
2) If the superuser credentials are not set, then the installer
assumes you are trying to add this to an existing database. Since
PL/PGSQL requires superuser privileges to add, we assume it is there
since we cannot add it.
I will review the documentation to try to ensure clarity on this matter.