Okay, we have new data.
This error comes from the way the ezsurvey tables are created. The TC says it is done using the survey wizard. It is NOT. If it was, this error would not occur.
The wizard uses the db_schema.dba file, with custom oracle settings from settings/dbschema.ini.append.php. In these settings, there is one that says that ezsurvey.title CAN be null, while the common schema file says it can't. The reason is that Oracle interprets NULL & empty string the same way.
I have understood after talking to the QA team that unlike what the TC says, the test system creates the tables differently.
As far as I'm concerned, the bug is invalid.