Another "log_min_duration_statement is ignored" question
Check individual users and / or dbs for settings that override server settings for logging:

smarlowe=# alter user smarlowe set log_statement='all';
ALTER ROLE
smarlowe=# alter database smarlowe set log_statement='all';
ALTER DATABASE
smarlowe=# \drds
                   List of settings
   Role   | Database |            Settings
----------+----------+---------------------------------
 smarlowe |          | log_statement=all
          | smarlowe | auto_explain.log_min_duration=1+
          |          | log_statement=all