It was one of the issues with Oracle 12c Release 1 that datapatch was not executed by dbca automatically. So, if you had installed patches to your Oracle home before running dbca, dbca did not take this into consideration and ran datapatch to apply the SQL changes to the databases. In August 2015 Mike Dietrich wrote a blog post on this issue.
So the general recommendation was: run datapatch after DBCA (and DBUA).
However, things have changed with Oracle 12c Release 2:
I recently made DBCA create the creation scripts and ran the scripts on the command line.
And the output was
[..] SQL> host /u00/app/oracle/product/184.108.40.206/OPatch/datapatch -skip_upgrade_check -db CDB12201; SQL Patching tool version 220.127.116.11.0 Production on Tue May 2 09:23:11 2017 Copyright (c) 2012, 2017, Oracle. All rights reserved. Connecting to database...OK Note: Datapatch will only apply or rollback SQL fixes for PDBs that are in an open state, no patches will be applied to closed PDBs. Please refer to Note: Datapatch: Database 12c Post Patch SQL Automation (Doc ID 1585822.1) Determining current state...done Adding patches to installation queue and performing prereq checks...done Installation queue: For the following PDBs: CDB$ROOT PDB$SEED Nothing to roll back Nothing to apply SQL Patching tool complete on Tue May 2 09:23:16 2017 [..]
OK, there is no PSU available for 18.104.22.168 at the moment, but it seems that the issue is solved and datapatch is executed automatically with Oracle 12c Release 2.