You can set a value on insert either by having a default value on a column or by having an insert/update trigger that sets the value in a column. So if the columns get a value on one database but not the other then they are by definition not exactly the same.
Here is some code that will help you to see if the table have a default value on the column in question.
set heading off;
set echo off;
Set pages 999;
set long 90000;
set linesize 120
col text format a115
accept object_type prompt "OBJECT TYPE:"
accept object_name prompt "OBJECT NAME:"
accept schema_owner prompt "SCHEMA OWNER:"
UPPER('&object_name'),UPPER('&schema_owner')) text from dual;