Yes, I confirm that there is an error. After deeper look the problem is related to making 'default' = NULL for CreatedById field.
The Export has the code which loads the objects and then goes through all Required fields which are empty and tries to preset them with a "sample_value" (not used much these days) or "no value" text (which is why CreatedById fails) and then tries to Validate it.
The whole issue can be fixed by adding:
'sample_value' => 'Guest' to declaration of CreatedById field.
Note that same bug is in Articles and other CategoryItems.