Hi Lakshmipathi,
The business has confirmed a peculiar way of updating partner information for one of their templates. (Not sure how they achieved this though)
Coming back to your question, yes, the change is reflecting even backwards (from delivery to sales order).
Anyways, this being neither a stnadard configuration or a regular requirement in general, I am closing this thread for now.
Many thanks for your time.
Regards,
Jagan