same createdDateTime when creating records
Could you react to my first question, please? As far as I know, change tracking isn't based on CreatedDateTime, therefore you seem to be solving a wrong problem.
The change tracking table will be updated when the transaction is committed. If you create both orders in the same transaction, they (and their change tracking entries) will became visible to the rest of the system at the same time (when the transaction gets committed).
Do you have some tests that prove me wrong?
CreatedDateTime isn't available in all tables and it doesn't have any information about updates, which change tracking takes into account.
Regarding your example, you're saying that you created SO2 and SO3 at almost the same time, but then you're saying that you want to export different orders together: SO3 and SO4. To me, it sounds like a very different scenario than what we discussed so far. You talked about orders created in the same transaction at the same time, while SO3 and SO4 were created twenty seconds apart. The fact that you created SO4 before SO3 and SO2 sounds suspicious too.
Which orders did you create in the same transaction?