pgaudit and create postgis extension logs a lot inserts

Hi,

I have installed pgaudit, and configured as:
pgaudit.log = 'ddl,role'
pgaudit.log_level = 'log' (default)

Versions: postgresql96 (9.6.6) , pgaudit96 (1.0.4), postgis 2.3.2, Rhel 7.4

When I then install postgis extension in a database it writes a huge amount of logs which slow down the server a lot.
Not only table creation and functions are logged, even all inserts in spatial_ref_sys are written to the audit-log.

LOG: AUDIT: SESSION,1,1,DDL,CREATE FUNCTION,,,"
......
INSERT INTO ""spatial_ref_sys"" (""srid"",""auth_name"
....

This behaviour make pgaudit useless in our environment due to the overhead in log-file write.
I have tried different combinations of pgaudit.log settings (role,-functions), (role), and also changed pgaudit.log_level to warning, but it was not better.

Does anybody have a useful pgaudit settings which not overflow the log files, even when installing postgis or other extensions?

Also noticed that setting a session log to none (set pgaudit.log='none';) overrides parameter from postgresql.conf, but does not get logged, and then you can do whatever you want without any audit.
I supposed this changing of audit session log parameter should be logged to file?

Regards,
Peter