Oracle 12.2 - Replacement of NOPARTITION feature
The (no)partition option for sequences was never documented. And thus never supported.
There was a bug in 12.1 which exposed this via dbms_metadata. It no longer happens in 12.2
Undocumented features can (and as this proves) do change without warning. Using them is strictly at your own risk.
If you do a dbms_metadata.get_ddl from database version 12.1 and want to use it in 12.2 then a NOPARTITION is supplied. Now we have to remove it.